Vascular filter device

ABSTRACT

A vascular filter device ( 1 ) has a support frame ( 2 ) and filter elements ( 4 ). The filter elements ( 4 ) extend from the support frame towards filter element ends forming an on-axis apex ( 5 ) at which they are interconnected by a holder ( 6 ). The filter elements ( 4 ) are biased such that if unconnected the filter element ends are located between the support frame and said central axis when the vascular filter device is unconstrained. The filter element unconnected positions are provided by the filter element shapes and the angles at which they extend from the support frame, and in one example this is achieved by laser cutting tubing and heat setting the material.

INTRODUCTION

The invention relates to a vascular filter of the type comprising asupport and a filter with filter elements connected at one end to thesupport and being interconnected at the other end. A typical example isconvergence of the filter elements in an apex. Examples are described inour prior patent specification numbers WO2008/010197, EP2208479,WO2010/082187, and US20100185227. In these examples the supportcomprises a proximal hoop and a distal hoop and interconnecting strutsbetween the hoops.

Many currently available devices are variations of a conical filterdesign that are prone to tilting as they have limited longitudinalsupport. Other variations include a design where a conical filter issupported caudally with an annular ring; such a design is also prone totilting as it has limited longitudinal support. This understanding issupported in clinical literature; reference Rogers, F. B., et al.,Five-year follow-up of prophylactic vena cava filters in high-risktrauma patients. Arch Surg, 1998. 133(4): p. 406-11; discussion 412.Upon advancement from a femoral approach, vascular geometry forces thedelivery catheter tip against the wall of the vena cava. Duringdeployment, the apex of the conical filter is released first and is freeto point into or along the vessel wall (i.e. the filter is in a tiltedposition during deployment). The filter does not expand until its mostcaudal end is released from the catheter. This instantaneous expansioncauses the filter to assume the tilted position of the deliverycatheter.

FIG. 1 shows a representation of a prior art device (70) such as thatillustrated in FIG. 52( j) of WO2008/010197. It has a support (72) andfilter elements (73) which are formed to extend longitudinally. Thefilter elements (73) are pulled radially inwardly and are interconnectedthrough the use of a holder. Prior art device in FIG. 4 of US20100185227is also similar with proximal support, distal support, a plurality ofsupport struts extending between the proximal and distal supports, and aplurality of filter elements interconnected with a holder. The filterelements are cantilevers and strain is produced at their connection tothe support when pulled radially inwardly. The filter element strain ishighest when the filter is constrained in the largest indicated vesseland reduces when constrained in smaller diameter vessels.

The invention is directed towards reducing strain between the filterelements and the support.

Another object is to reduce risk of fibrin growth and/or thrombusformation at the filter element interconnection.

SUMMARY OF THE INVENTION

In the invention, the vascular filter device has a support structurewhich is preferably stent-like in overall configuration, and preferablyhas proximal and distal supports linked by connecting struts. The devicepreferably has a filter with filter elements connected to the support atone end and converging at the other end. In some embodiments theyconverge at an apex. The area of convergence may be interconnected usinga variety of coupling means or the area of convergence may be integralwith at least some of the filter elements.

In one embodiment the support and filter elements may be integralwherein the filter elements are interconnected at the area ofconvergence using a coupling means such as pins, caps, rings, welds,ties or snap fitting arrangements. This induces strain in thecantilevered filter elements during use in a blood vessel that isdistributed where the filter elements are connected to the filter frame.The invention addresses this problem using shape setting and/orannealing steps to improve durability, referred to as fatigueperformance in this document, and teaches methods to provide a morestreamlined profile of the apex to enhance blood flow characteristics.This embodiment is referred to as ‘Shape Set Filter Elements’ in thisdocument.

In another embodiment the support and/or filter elements may not beintegral wherein the filter apex is integral with at least some of thefilter elements. The integral apex enhances blood flow characteristicsat the apex by providing a more streamlined profile while providingincreased manufacturing efficiency and reduced manufacturing coststhrough elimination of joints at the apex. The invention also includesshape setting and/or annealing steps to reduce strain where the filterelements are connected to the support frame. This embodiment is referredto as ‘Integral Apex’ in this document.

In a further embodiment the support frame, filter, and filter apex areintegral wherein the device is formed from a single piece. The integralapex provides a more streamlined profile to enhance blood flowcharacteristics at the apex while the single piece design providesincreased manufacturing efficiency, reduced manufacturing costs andimproved durability, referred to in this document as fatigueperformance, as no joints are required in the device. Shape settingand/or annealing steps are also taught to reduce strain where the filterelements are connected to the support frame. This embodiment is referredto as ‘Integral Filter’ in this document.

In this specification the terms “proximal” and “distal” are withreference to the direction of blood flow, the proximal parts beingupstream of the distal parts.

A vascular filter comprises:

one or more filter elements for capturing thrombus passing through ablood vessel, andone or more support members for supporting the one or more filterelements relative to a wall of the blood vessel.

By capturing the thrombus, the filter prevents the thrombus from passingto the heart or lungs, which may cause pulmonary embolism. By supportingthe capture members this ensures that the filter elements are maintainedin the desired location in the blood vessel.

The invention provides means to eliminate and/or reduce tilting,perforation and migration. The present invention overcomes tiltingthrough application of a longitudinal support structure. In order toprovide an effective filter, the longitudinal support is designed toinclude minimum implant length. The term “implant length” refers to thelength of vessel required to implant a device. A device with lessimplant length is desirable as it will be suitable for patients withshorter vessels. Referring to FIG. 77, excessive filter length in a venacava is unfavourable as it can lead to obstruction of the renal veinwhich in time may lead to thrombosis. Also, some patients have shortervena cavae than average which would prevent the use of a filter withexcessive implant length. The longitudinal support structure of thepresent invention is designed to expand immediately as it is unsheathedwhen deployed from a femoral or jugular approach. For example, whendeploying from a femoral approach, a portion of the longitudinal supportis expanded and pressed against the vessel wall when the cranial half ofthe device is uncovered, this step actively pushes the cranial end ofthe delivery catheter (with the caudal end of the device sheathed) awayfrom the vessel wall to remove delivery induced tilting. As the proximalend of the device is unsheathed, it is now located centrally in thevessel and the immediate expansion of the proximal support ring assumesits cylindrical configuration. Tilting is a well known complication ofIVC filters and is associated with complications including IVCperforation, migration and reduced capture efficiency.

Perforating filters can cause injury to nearby organs leading to severediscomfort, injury, and/or death of the patient. Tilted filters have atendency to perforate as the apex of the conical filter or other freeended struts point into the vessel wall. When a filter is tilted, notonly are its barbs out of contact with the vessel wall, its radial forceis unevenly distributed against the vessel wall. The filter is operatingwithout adequate vessel securing means and is at high risk formigration. Migration of a filter to the heart can cause massivepulmonary embolism. The uneven force distribution also leads to fatigueand fracture of the device as it is subjected to increased localisedstrains. Vena cava filters experience deflections at a rate of 70/minradially and 20/min longitudinally due to pulsatile blood flow andrespiration respectively—these deflections exacerbate the risks ofperforation, migration, and fracture of a tilted filter.

Reduced capture efficiency is a consequence of tilted filters as theapex of the filter cone drifts off centre. Peak flow velocities are inthe centre of the vessel for uniform blood flow and it is through thesepeak velocities that blood clots flow. Therefore, vena cava filters aredesigned to have higher filter efficiency at the centre of the vessel.As the apex of a tilted filter moves to one side of the vessel, largeropenings (designed to be positioned at the periphery of the device) movetowards the centre of the vessel and reduce the capture efficiency ofthe device.

Tilting of the filter is also expected to reduce the effectiveness oflysis which is the physiological process in which the captured clots arebroken down in the body. This expectation is due to captured clots beingdirected to the vessel wall, away from peak flow velocities in thecentre of the vessel. Holding the clot centrally in the vena cava isunderstood to provide optimal conditions for lysis. The ratio of filterlength to vessel diameter should range from 1:1 to 2.3:1 when deployedin the filters maximum indicated vessel diameter to prevent tilting.More preferably, the ratio of filter length to vessel diameter shouldrange from 1.5:1 to 2:1. The longitudinal support is designed to pressagainst the vessel wall with sufficient radial force to preventmigration in the vessel. The support may also be fitted with barbs orprotrusions to aid in anchoring it to the vessel wall.

The filter elements connect to the apex in a way that minimisesobstruction to the blood flow, for instance, it is preferred that two ormore filter elements merge into one filter element in close proximity tothe apex in order to provide a streamlined connection (refer to FIGS. 2,7, 27, 29, 30, 47, 48, 61, 62, 67 and 76 a to 76 c). The proximity ofthe merging point to the apex should range from 1 to 10 mm; a range of 3to 6 mm is preferred.

In another aspect, a vascular filter comprises:

a support frame and an array of filter elements,the filter elements extending from the support frame towards a centralapex,the filter element ends being located between the support frame and acentral axis of the filter,wherein the filter element ends are interconnected.

The invention affords improvements to the art by disclosing a filterthat enhances fatigue resistance of a vena cava filter.

The invention also provides an interconnected filter apex with a morestreamlined profile to improve blood flow characteristics. Refer toFIGS. 5, 12 to 19, and 80 to 139. The streamlined profile reducesirregular flow patterns to prevent the formation of fibrin growth andblood clots. The formation of blood clots on permanent filters is wellknown in the art to occur after implantation. Additionalantitrombogenicity can be achieved by including an antithrombogeniccoating on at least part of the surface of the filter elements and apex.Such coatings include but are not limited to hydrophilic, hydrophobic,heparin or other thrombo-resistant pharmacological coatings.

Durability, referred to as fatigue resistance in this document, isenhanced by reducing the deflection and consequent loading/strain of thefilter elements relative to the support frame. The deflection prior toloading can be reduced for a filter designed for a particular vesselsize by shape setting the filter elements to form a central apex whenconstrained in the indicated vessel size without interconnection betweenthe filter element ends. This is advantageous for support frame designsthat include a hoop distal to the filter element ends as in most cases,the filter element ends will be free to move relative to each other andneed to be pulled radially inwardly in order to form a central apex. Theforce required to form the central apex results in strain where thefilter elements connect to the support frame. Reducing the deflectionrequired to form a central apex reduces the force and resultant strain.

In another embodiment, the filter is indicated across a vessel sizerange, preferably from 16 to 32 mm internal diameter. For thisembodiment, deflection is relative to the vessel that the filter isconstrained in. Taking a filter that is indicated for blood vesselsranging from 16 to 32 mm internal diameter, it is preferred that thefilter elements are shape set to form a central apex when constrained ina vessel midway (24 mm) across the vessel size range. Then, thedeflection of the interconnected filter element ends is equal whenconstrained in the lower (16 mm) and upper (32 mm) vessel sizes, thefilter elements bending radially outwardly in the lower vessel size andthe filter elements bending radially inwardly in the upper vessel size.Another way of describing this embodiment is that the filter elementends will be positioned a quarter way between a central axis and thesupport frame when constrained by the upper vessel size of 32 mm.Similarly, filters for other vascular applications may be sized forvessels in the range of 3 mm to 12 mm.

A preferred embodiment is indicated across a vessel size range,preferably from 16 to 32 mm internal diameter, sized in this example tosuit the vena cava, with filter elements that extend radially inwardlyso that their ends are positioned at a point radially outwardly of aquarter way position between a central axis and the support frame whenconstrained in the upper vessel size of 32 mm. This embodiment balancestensile strain between the upper and lower vessel sizes and accounts forthe influences of the filter element centroid.

These embodiments are advantageous for support frame designs with andwithout distal support hoops as all marketed filter devices areindicated across a vessel size range and hence devices including supportframes with filter elements interconnected at a central apex tend tohave maximum strains in the upper vessel size and minimum strains in thelower vessel size due to the filter elements bending radially inwardlyrelative to the support frame. This is because their form must favor theupper vessel size unconstrained in order to apply sufficient radialforce against the vessel wall. It is appreciated that this may bereversed in that the filter element ends may be heat set with their endsforming a central apex and the filter elements are deflected radiallyoutwardly relative to the support frame in the lower vessel sizeincluding support frame designs with and without distal support hoops.The embodiments disclosed are advantageous for these designs in thatthey tend to have max strains in the upper vessel size and minimumstrains in the lower vessel size as their form must favor the uppervessel size unconstrained.

The interconnection between the filter element ends may be supplied byway of a holder or by interlocking features attached to or part of thefilter element ends.

In another aspect, a vascular filter comprises:

one or more filter elements for capturing thrombus passing through ablood vessel, andone or more support members for supporting the one or more filterelements relative to a wall of the blood vessel, wherein at least one ofthe filter elements is integral with the filter apex.

The invention reduces fibrin formation and clot build up throughimproved blood flow characteristics by providing an integral filter apexthat eliminates filter element joints at the filter apex. Such aconstruction minimizes obstruction to blood flow by providing astreamlined profile and reduces irregular flow patterns to prevent theformation of fibrin growth and blood clots. Refer to FIGS. 27 and 62.The formation of blood clots on permanent filters is well known in theart to occur after implantation. Additional antitrombogenicity can beachieved by including an antithrombogenic coating on at least part ofthe surface of the filter elements and apex. Such coatings include butare not limited to hydrophilic, hydrophobic, heparin or otherthrombo-resistant pharmacological coatings.

In another aspect, a vascular filter comprises:

one or more filter elements for capturing thrombus passing through ablood vessel, andone or more support members for supporting the one or more filterelements relative to a wall of the blood vessel, wherein the device ismanufactured from a single piece.

The present invention discloses a blood filter that is manufactured inone piece to provide an integral filter. Advantages of an integralfilter include increased manufacturing efficiency, reduced manufacturingcosts and improved durability, referred to in this document as fatigueperformance, as no joints are required in the device. The locations ofjoints frequently coincide with failure locations when devices aresubject to cyclical loading.

According to another aspect, the invention provides a vascular filterdevice comprising a support frame and filter elements,

-   -   the filter elements extending from the support frame towards        filter element ends forming an apex at which they are        interconnected,    -   wherein said apex is located at or near a central axis of the        vascular filter device; and    -   wherein the filter elements are biased such that if unconnected        the filter element ends are located between the support frame        and said central axis when the vascular filter device is        unconstrained.

The filter elements thus have a natural position which leads to littlestress in use while they are interconnected at the apex. This isparticularly advantageous in light of the conditions with high frequencyexpansion and contraction as set out above in the introduction.

In one embodiment, the support frame and the filter elements are formedintegrally. In one embodiment, the support frame and the filter elementsare formed from NiTi.

In one embodiment, the filter element unconnected positions are providedby the filter element shapes and the angles at which they extend fromthe support frame.

In one embodiment, the filter elements have positions if unconnectedsuch that the filter element ends are located approximately 10% to 50%of the distance from the central axis to the support frame. In oneembodiment, the position is approximately 15% to 40% of said distance.

In one embodiment, the vascular filter device has an indicated vesselsize range, and wherein the filter elements are biased to have positionsif unconnected such that:

-   -   (a) when the device is constrained in a vessel which lies in an        upper sub-range of said indicated range, the filter element ends        are between the central axis and the support,    -   (b) when the device is constrained in a vessel which lies in a        central sub-range of said indicated range the filter element        ends are approximately on the central axis, and    -   (c) when the device is constrained in a vessel which lies in a        lower sub-range of said indicated range the filter element ends        extend through said central axis.

In one embodiment, the filter elements have similar maximum strains insituations (a) and (c) when the filter element ends are interconnected.

In one embodiment, the filter elements have approximately equal maximumtensile strains in situations (a) and (c) when the filter element endsare interconnected.

In one embodiment, the support frame comprises a proximal hoop, a distalhoop, and interconnecting struts.

In one embodiment, the proximal hoop has peaks and the filter elementsare connected to the support at or adjacent distal peaks of the proximalhoop.

In one embodiment, the filter element ends, the filter elements, and thesupport frame are formed integrally from one piece.

In one embodiment, the filter element ends are formed integrally toprovide an integral apex.

In one embodiment, the filter element ends are interconnected by aholder.

In one embodiment, at least some filter elements have eyelets and theholder is trained through the eyelets.

In one embodiment, the holder has an integral fastener.

In one embodiment, the holder is in the form of a spiral in which spiralturns are in contact or in close proximity with each other to providethe integral fastener.

In one embodiment, the holder is in the form of a planar spiral in whichthe spiral turns overlap in the radial direction.

In one embodiment, the holder is in the form of a three-dimensionalspiral in which the spiral turns overlap at least partly in the axialdirection.

In one embodiment, the outer diameter of the holder is tapered axially.

In one embodiment, the spiral has between 1 and 2 turns.

In one embodiment, the spiral is formed from a length of material havingtapered ends.

In one embodiment, the holder comprises a clip formed from a body havingone end which fits into the other end.

In one embodiment, the holder comprises a length of material forming aloop at one end and free ends of the length form a hook extendingthrough the loop.

In one embodiment, the free ends are tied in a knot or are welded toprevent release of the holder.

In one embodiment, the free ends are engaged through at least one filterelement end eyelet at least twice.

In one embodiment, the holder comprises a plurality of prongs which aredirected radially inwardly and are arranged to engage with filterelement eyelets.

In one embodiment, the prongs and filter element ends are arranged to becrimped together for fastening the filter element ends.

In one embodiment, the prongs are directed distally at their ends.

In one embodiment, the prongs have features for snap-fitting into thefilter element eyelets.

In one embodiment, the holder comprises at least one hook engagingfilter element eyelets.

In one embodiment, said hooks are mounted on a ring or disk-shapedholder base.

In one embodiment, there is a pair of hooks on opposed sides of thecentral axis, each arranged to engage a plurality of filter elementeyelets.

In one embodiment, said hooks extend in a radial plane only.

In one embodiment, the holder is S-shaped.

In one embodiment, the holder is in the form of a split ring.

In one embodiment, the split ring has ends forming a non-reentrantopening.

In one embodiment, the holder includes at least one abutment to preventthe filter elements from dislodging.

In one embodiment, the holder includes a sacrificial length arranged toaid entrainment through the filter element eyelets and wherein thesacrificial length is removed after assembly.

In one embodiment, the holder comprises a central hub with slots toaccommodate filter elements and a clamping ring to retain the filterelements in said slots.

In one embodiment, the filter elements are interconnected byinterlocking features, such as slots and ridges or dovetail features.

In one embodiment, the filter elements are magnetically interconnected.

In one embodiment, the interlocking features are integral with thefilter elements.

In one embodiment, the holder has one or more annular sockets to receivethe ends of the filter elements.

In one embodiment, the holder is crimped.

In one embodiment, the device comprises two parts which are connectedtogether at a connection.

In one embodiment, the connection is in the struts.

In one embodiment, the connection is at the proximal end, at the distalend, or between said ends.

In one embodiment, the connection is between the filter and the support.

In one embodiment, the connection is within the filter.

In one embodiment, the parts are connected by a connector including asleeve which receives two members.

In one embodiment, the connection comprises device members butt joinedtogether.

In one embodiment, the connection comprises overlapping device members.

In one embodiment, the connection comprises male and female connectors.

In one embodiment, the connection comprises a joint allowing mutualpivoting.

In one embodiment, the sleeve comprises formations to engage withmembers inserted into the sleeve.

In one embodiment, the formations are arranged for snap-fitting of themembers within the sleeve.

In one embodiment, the filter elements extend towards two or more filterapexes.

In one embodiment, the filter apexes are joined.

In one embodiment, the device is formed from laser-cut tubing and thediameter of the joined filter apexes is less than that of the tubing.

In one embodiment, the filter apex interconnection is arranged toprovide flexibility in the axial direction and/or the radial direction.

In one embodiment, the filter apex interconnection is C-shaped in axialview.

In one embodiment, the filter apex interconnection is formed to receivean array of connector struts when the device is compressed beforedelivery.

In one embodiment, the device is formed from laser-cut tubing and thetubing diameter is greater than the diameter of the filter apexinterconnection.

In one embodiment, the filter apex interconnection is formed from anecked-down region of the tubing.

In one embodiment, the two parts are cut from a single tube.

In another aspect, the invention provides a vascular filter devicemanufactured from a single piece of raw material.

In one embodiment, the filter or the support is inverted from a naturalposition during manufacture so that the filter lies within a spaceencompassed by the support frame.

In one embodiment, at least some filter elements are connected to thedistal hoop.

In one embodiment, the proximal and distal hoops comprise at least onesinusoid, crown, or zigzag pattern.

In one embodiment, the distal hoop comprises an array of V-shaped strutsand wherein the V-shaped struts are not directly interconnected.

In one embodiment, the distal hoop comprises an array of V-shaped strutsand extension struts connecting the array of said V-shaped struts to theconnector struts.

In one embodiment, the distal hoop comprises an array of M-shapedstruts.

In one embodiment, the distal hoop comprises an array of closed cells.

In one embodiment, an array of twin connector struts interconnect saidhoops.

In one embodiment, each twin connector strut is not connected at thedistal and proximal ends forming an opening in the array of cellsbetween the struts of the twin connector strut and separating theproximal support hoop into an array of v-shaped or m-shaped struts.

In one embodiment, the proximal hoop comprises an array of cells andwherein an array of twin connector struts interconnect said hoops,wherein each twin connector strut is not connected at the distal andproximal ends forming an opening in the array of cells between thestruts of the twin connector strut and separating the distal supporthoop into an array of V-shaped or M-shaped struts, and wherein thefilter elements extend between the struts of the twin connector strut.

In one embodiment, the filter elements are connected to the supportframe via an array of distally pointing V-shaped struts.

In one embodiment, the proximal hoop comprises two crowns, and whereinthe filter elements are connected to the distal peaks of the proximalhoop.

In one embodiment, the V-shaped struts of the distal hoop pointdistally, and wherein each V-shaped strut is connected to the proximalhoop via two connector struts.

In one embodiment, an array of V-shaped filter elements extend to anintegral apex between adjacent V-shaped struts of the distal hoop.

In one embodiment, the V-shaped struts of the distal hoop pointproximally and wherein each V-shaped strut is connected to the proximalhoop via one connector strut.

In one embodiment, the filter elements are connected to the connectorstruts at points distally of the extension strut connection.

In one embodiment, the filter elements are connected to the connectorstruts at positions proximally of the extension strut connection.

In one embodiment, there are two extension struts for every connectorstrut.

In one embodiment, there is one connector strut for every M-shaped strutand wherein the ends of adjacent M-shaped struts are joined.

In one embodiment, the closed cell is diamond shaped and the array ofconnector struts are connected to the proximal peaks of the diamonds.

In one embodiment, the cells are diamond shaped and an array of twinconnector struts are connected to the distal peaks of said cells.

In one embodiment, some of said filter elements are supported only byother filter elements.

In one embodiment, additional filter elements extend from the apexinterconnection and are not connected at their proximal ends.

In one embodiment, at least some of the support struts have free distalends.

In one embodiment, the support frame comprises longitudinal struts whichare not straight in configuration.

In one embodiment, the filter elements are formed to have alength-reducing shape or at least part of the support can be lengthenedso that the apex interconnection lies between the most proximal anddistal ends of the support when in the expanded state.

In one embodiment, the ratio of filter length to support frame diameterranges from 1:1 to 2.3:1 when the device is unconstrained.

In one embodiment, the ratio of filter length to support diameter rangesfrom 1.5:1 to 2:1 when the device is unconstrained.

In one embodiment, a portion of the support is flared outwardly.

In another aspect, the invention provides a method of manufacturing avascular filter device comprising a support frame and filter elements,

-   -   the filter elements extending from the support frame towards        filter element ends forming an apex at which they are        interconnected, wherein said apex is located at or near a        central axis of the vascular filter device; wherein the filter        elements are biased such that if unconnected the filter element        ends are located between the support frame and said central axis        when the vascular filter device is unconstrained,        wherein the method comprises the steps of:    -   providing a tubing, cutting the tubing, and expanding the        tubing.

In one embodiment, the filter elements are heat-treated to provide saidpositions.

In one embodiment, the support frame comprises a proximal hoop and adistal hoop and said hoops are interconnected by longitudinal supportstruts, and said hoops and struts are formed by cutting of said tubing.

In one embodiment, the cut tubing is expanded to form the filter andheat set to remember a permanent shape.

In one embodiment, the tubing is expanded after cutting to provide a newshape and is constrained in a fixture or on a mandrel for heattreatment.

In one embodiment, the device is crimped down to a diameter that isgreater than, equal to, or less than that of the tubing and loaded intoa delivery sheath for low profile delivery to the implant site.

In one embodiment, the tubing is of a shape-memory material so that whendeployed into an environment that is above an Af temperature, the devicewill revert to its expanded form provided by the shape setting step.

In one embodiment, the material is annealed to remove stresses raisedthrough work hardening.

In one embodiment, the tubing diameter is greater than the radialdimension of the apex interconnection.

In one embodiment, the filter apex interconnection is formed from anecked-down region of the tubing.

In one embodiment, the tubing is cut to provide two parts which aresubsequently interconnected at a connection.

In one embodiment, the filter or the support is inverted from a naturalposition during manufacture so that the filter lies within a spaceencompassed by the support.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be more clearly understood from the followingdescription of some embodiments thereof, given by way of example onlywith reference to the accompanying drawings in which:—

FIG. 1 is a side view and an end view of a filter device of the priorart as discussed above, the top image illustrating the device with thefilter element ends unconnected, the bottom image illustrating thefilter element ends interconnected;

FIG. 2 is a set of oblique views of a device of the invention, the leftimage illustrating the device with the filter element ends unconnected,the right image illustrating the filter element ends interconnected;

FIG. 3 is a plan, elevation, and end view of a device of the inventionunconstrained with filter element ends unconnected and convergingtowards an apex at early stages of manufacture;

FIG. 4 is a plan, elevation, and end view of a device of the inventionunconstrained with the filter element ends interconnected to form anapex at early stages of manufacture;

FIG. 5 is an oblique view of the filter element ends interconnected toform an apex with a holder;

FIG. 6( a) is a set of side and end views of a device of the inventionat early stages of manufacture constrained in a Ø32 mm and Ø24 mm tube,and FIG. 6( b) is a diagram illustrating the preferred filter elementend positions at an early stage of manufacture before assembly with aholder when constrained in vessels with different vessel diameters;

FIG. 7 is a set of views showing a v-shaped filter element on the leftand two single filter elements on the right;

FIG. 8 is a set of side views of the prior art showing only top andbottom filter elements, in which the top image depicts the filterelements in a relaxed state without a holder when constrained in avessel while the bottom image depicts the filter elements pulledradially inwardly;

FIG. 9 is a set of side views of the present invention showing only topand bottom filter elements, in which the top image depicts the filterelements in a relaxed state without a holder when constrained in avessel. Dotted lines depict the filter elements forming a central apex,and the bottom image depicts the filter elements in a relaxed state withparametric designations;

FIG. 10 is a set of cross sectional views of a filter element of thepresent invention, in which the image to the left depicts the filterelement profile as cut from a raw tube shown in broken lines, and imageto the right gives parametric designations to the cross section;

FIG. 11 is a cross sectional view of a filter element of the presentinvention with further parametric designations;

FIG. 12 is a cross-sectional side view of crimping of the filterelements at the apex,

FIGS. 13 and 14 show how a pin may be used for this purpose, and

FIG. 15 shows the use of a multi-lumen tube for this purpose;

FIG. 16 shows two types of holder caps for retaining the filter elementat the apex;

FIG. 17 shows how the filter elements may be twisted together;

FIG. 18 shows filter elements which are configured at their ends forinterconnection;

FIG. 19 shows such interconnection with dovetail inter-locking;

FIG. 20 is a perspective view of a filter device of the invention duringmanufacture, and

FIGS. 21 and 22 show parts in greater detail;

FIGS. 23 and 24 show expanded parts of the device, and

FIG. 25 shows the parts connected together;

FIG. 26 shows the laser cut pattern;

FIG. 27 shows the assembled device and highlights the integral apex;

FIG. 28( a) shows an integral proximal support, filter arms and apexwith a separate distal support and connector arms and FIG. 28( b) showsa separate support and integral filter elements and apex;

FIG. 29( a) shows a separate support and FIG. 29( b) shows a separatefilter, and

FIGS. 30 and 31 show the assembled device;

FIG. 32 shows a device in which the distal hoop is provided as aseparate piece, and

FIG. 33 shows a device in which the connection points are on the filterelements;

FIGS. 34 to 41 show various methods of making the connections;

FIGS. 42 and 43 show methods of reducing the crimped outer diameter;

FIGS. 44 to 47 show an arrangement in which the filter apex is connectedto a distal support hoop;

FIGS. 48 to 53 show embodiments in which the apex is not fully closed inshape in axial view;

FIGS. 54 to 57 show different arrangements of connector struts;

FIGS. 58 to 60 are each a pair of side and end views of filter devicesof the invention;

FIG. 61 is a set of plan, elevation, end and perspective views of afurther device of another embodiment;

FIG. 62 is a set of side, end, and perspective views of an integral apexof one embodiment;

FIG. 63 is a laser cut pattern for a device of one embodiment;

FIG. 64 is a side view and end view of a device of an alternativeembodiment;

FIG. 65 is a pair of views showing filter element connections of devicesof alternative embodiments;

FIG. 66 is a side and end view of a further device;

FIG. 67 is a set of side and laser cut pattern views of the device shownin FIG. 66;

FIG. 68 is a view of an alternative filter element;

FIG. 69 is a view of an alternative connector element;

FIGS. 70 to 74 are each a side view and an end view of alternativefilter devices of the invention;

FIG. 75 is a set of plan, elevation, and end views of a further deviceof the invention;

FIGS. 76 a and 76 b are perspective and laser cut pattern views of thedevice shown in FIG. 75 respectively;

FIG. 76 c is a view of an alternative laser cut pattern of the deviceshown in FIGS. 75 to 76 b;

FIG. 77 is a view of the Inferior Vena Cava (IVC) showing the iliacveins, renal veins and implant length for a device of the invention;

FIGS. 78 to 79 are each a set of plan, elevation and end views ofalternative filter devices of the invention;

FIG. 80 and is a perspective view of a holder of one embodiment, forinterconnecting or holding the filter element ends together in an apex,in which the holder is formed by a spiral;

FIG. 81( a) is a perspective view of an alternative spiral holder, andFIGS. 81( b) and 81(c) show this holder in use;

FIGS. 82, 83 and 84 are perspective views showing alternative holders ofthe overlapping spiral or “key ring” type;

FIGS. 85 to 93 are perspective views of holders which can be trainedthrough eyelets of filter element ends but are not of the overlappingspiral type,

FIG. 85 showing a holder of the split ring type,

FIGS. 86 and 87 showing holders in which one end forms a hook whichpasses through a loop at the other end,

FIG. 88 shows another holder of the split ring type, and

FIGS. 89 to 93 show holders in which a male end fits into an opposedfemale end;

FIGS. 94 to 97 show holders which have prongs for extending throughfilter element end eyelets and are biased radially inwardly for closure;

FIG. 98 is a perspective view of a holder which has prongs directedradially inward for engagement in eyelets such as the type shown in FIG.99, as shown in FIGS. 100 to 102;

FIG. 103 shows a variation in which the prongs extend both radiallyinward and are turned to be partly on-axis for engagement with eyeletsas shown in FIGS. 104 and 105;

FIG. 106 shows an alternative holder, with a completely on-axis prongend and FIGS. 107 and 108 show it in use;

FIG. 109 shows a further holder, again having inwardly radially-directedprongs, and

FIGS. 110 to 112 show this holder in use, in which FIG. 112 is across-sectional view showing snap-fitting engagement of the prongsthrough the filter element end eyelets;

FIG. 113 shows an alternative holder, having hooks on an annular base,there being one hook per filter element end, and

FIGS. 114 to 116 show this in use;

FIG. 117 shows a holder having two arcuate hooks in a plane through thedevice and being on an on-axis ring base, each hook being configured toaccommodate half of the filter element ends, and

FIGS. 118 to 120 show the holder in use;

FIG. 121 shows a holder with two opposed hooks in an arrangement broadlysimilar to that of FIGS. 117 to 120, except that the hooks extend fromopposite ends of a common radially-extending member to form an S-shape,and

FIGS. 122 and 123 show the holder in use;

FIG. 124 shows a holder which is similar in principle to the holder ofFIG. 121, the main difference being that the ends of the hooks are moreturned-in, and

FIGS. 125 and 126 show it in use;

FIG. 127 shows a further variation in which the ends of the hooks haveabutments which are turned on-axis, and

FIGS. 128 and 129 show it in use;

FIG. 130 shows a holder in the form of a C with the ends turned in toform a non-re-entrant opening, and

FIGS. 131 and 132 show it in use; and

FIGS. 133 to 139 show an alternative holder, in two parts having acentral core which fits between the filter element ends and an outerring which fits over the core and the filter element ends to clamp themtogether to form an apex.

DESCRIPTION OF THE EMBODIMENTS Shape Set Filter Elements

Referring to FIGS. 2 to 6 a vascular filter device 1 of the presentinvention is manufactured by providing a part 2 with a support 3 andfilter elements 4 which are formed to bend inwards and converge towardsa central apex. The filter elements s are interconnected using a holder6 to form a central apex 5 on a central axis of the device.

In more detail, in one embodiment the filter device 1 is formed from alaser cut NiTi shape memory alloy tube by expanding and constraining thedevice in a fixture or on a mandrel and then performing a heat treatmentstep to set the new shape. This method is referred to here as shapesetting. The device can then be crimped down to a diameter that isgreater than, equal to, or less than that of the raw tube and loadedinto a delivery sheath for low profile delivery to the implant site.When deployed into an environment that is above the Af temperature, thefilter will revert to its expanded form provided by the shape settingstep (for example, if the material's Af temperature is 20° C., it willrevert to its shape set form in an environment that is above 20° C. suchas that of blood at 37° C. It is appreciated that materials withoutshape memory properties may alternatively be used. In this embodiment,the filter elements can be manually formed into a shape and then heattreated, annealed, to remove stresses and strains introduced throughwork hardening. The preferred embodiment uses shape memory materials asthey are capable of withstanding much higher strains.

Improvements are made to the prior art device in that the presentinvention reduces filter element strain at the connection to the supportframe. Vena cava filters operate in an environment in which the filterexperiences deflections at a rate of approximately 70/min radially andapproximately 20/min longitudinally due to pulsatile blood flow andrespiration respectively. Therefore, reduced filter element strain willimprove durability, fatigue performance and fracture resistance. Inorder to reduce filter element strain during use in a blood vessel, thefilter may be shape set with the filter elements forming the centralapex without a coupling means when constrained in the indicated vesselsize. This would remove filter element strain when the filter device isplaced in a blood vessel of the indicated vessel size as the filterelements would be in a relaxed state along their length and at theconnection to the support frame. It is beneficial to oversize the devicein order to provide sufficient radial force that will prevent migrationand enhance deployment accuracy. The device over sizing should beapplied in a balance so as not to provide excessive radial force thatmay cause transmural migration (movement of the device through thevessel wall) or perforation. With an oversized device, the filter shapesetting step should provide filter element ends that form a central apexwhen constrained in the intended vessel size indication without the useof a coupling means to interconnect the filter elements at an apex. Theshape setting step may be sufficient to keep the filter closed onceadequate stiffness is attributed to the filter elements so that theyexhibit no movement or minimal movement upon impact of a blood clot. Inanother embodiment, a coupling means is added to strengthen the apex towithstand the impact of blood clots and vessel movement. The couplingmeans may be provided by way of a holder or a feature(s) on the filterelements that interconnect the filter elements.

The device of the present invention may be indicated across a vesselsize range, ideally from 16 mm to 32 mm internal diameter. In thisembodiment, the filter may be shape set with the filter elements curvedradially inwardly so that the filter element ends are positionedapproximately one quarter of the way between the central apex and thevessel wall (4 mm) if the filter part 2 is constrained in the uppervessel size of 32 mm. Alternatively, the filter may be shape set withthe filter elements curved radially inwardly so that the filter elementends form a central apex if the filter part 2 is constrained in themiddle vessel size of 24 mm. Both situations are illustrated in FIG. 6(a) and FIG. 6( b). Then, the filter elements will have similar strain(in opposite bending directions) when placed in a 16 mm or 32 mm vessel.For example, if the filter device was constrained in the minimumindicated vessel of ID of 16 mm, the filter element ends would extendpast the central axis as shown in FIG. 6( b)—approximately one quarterof the way (4 mm) from the central axis to the opposing vessel wall.However, when the filter element ends are coupled together using aholder, the filter elements press against opposing filter elements(applying compressive forces)—this is in contrast to when the filter isconstrained in the maximum indicated vessel size of 32 mm where thefilter elements pull against opposing filter elements (applying tensileforces). The diameter to form a central apex may be offset from themiddle of the vessel range to account for structural considerations andensure strains are similar when the device is implanted in the minimumand maximum indicated vessel sizes (i.e. equal or similar strain may beachieved when the filter elements are offset from the middle of thevessel size range due to offset centroid positions inherent in differentfilter element cross section profiles). In another embodiment, thediameter set to form a central apex may be chosen based on the mean ofvessel sizes recorded in the literature in order to achieve minimumstrain for the majority of implantations.

FIG. 7 is a pair of views comparing a V-shaped filter element to twosingle filter elements. Provided that b and h of the V-shaped filterelement are equal to b and h of the two single filter elements, anapproximation can be made that the second moment of area, I, for theV-shaped filter element is equal to that of two single filter elements.

By way of comparison, FIG. 8 a is a side view of the prior art deviceshowing only the top and bottom filter elements in a relaxed statewithout the use of a holder when constrained in a vessel. The top andbottom filter elements are shown without the support frame for clarity.The proximal end of the filter elements are assumed to be in a fixedposition as they are attached to the support frame. FIG. 8 b is a sideview of the prior art device showing only the filter elements with aholder coupling the filter element ends to form a central apex whenconstrained in a vessel. Also shown is the force, P, and deflection, δ,required to pull a filter element radially inwardly to the central apex.Assuming the filter element is a straight cantilever beam with uniformcross section, the filter element deflection, δ, is defined below whereL is the axial length between the connection to the support frame andthe filter element end, E is Young's modulus for the filter elementmaterial, and I is the second moment of area.

δ=PL ³/3EI

The strain on the surface of the filter element in bending at a point L₁is

ε=My/EI=Mt/2EI where the moment M=L ₁ P

Then,

ε=3tδL ₁/2L ³

Filter element strain is highest at the connection to the support framewhere L₁=L. Filter element length is determined by balancing capturespace (the volume of the capture cone increases with increasing filterelement length) and parking space (parking space increases withincreasing filter element length). Limited by the range of filterelement lengths that will be adequate for capture space and parkingspace, it is preferred to control filter element strain by varyingfilter element thickness and/or deflection. Deflection is determined byvessel size for the prior art device leaving only the filter elementthickness for strain control. Filter element strain reduces withdecreasing filter element thickness; however, filter element thicknessshould be kept high enough to contribute sufficient radial force inorder to prevent the filter device from migrating.

In order to improve the fatigue resistance, the present inventionreduces the deflection, δ, in order to reduce the resultant strain.

FIG. 9 a shows a simplified filter element profile of the presentinvention (support frame not shown). The relaxed filter element positionin the upper vessel size is shown alongside the interconnected filterelements illustrated with broken lines. Assuming the filter element is astraight cantilever beam with uniform cross section, the bendingequations can be described using Castiglianos thin curved beam theorem:

$\delta_{n} = {\frac{\delta \; U}{\delta \; P_{n}} = {{\int{{\frac{M}{EI} \cdot \frac{\delta \; M}{\delta \; P_{n}}}{x}}} = {\int{{\frac{M}{EI} \cdot \frac{\delta \; M}{\delta \; P_{n}} \cdot r}{\beta}}}}}$

Where, U=energy, P=force, M=moment, E=modulus, I=second moment of area,x=length, r=radius of arc, β=angle of arc, δ=deflection

FIG. 9 b shows angular relationships for the simplified filter elementprofile. The simplified filter element is shape set with an initialradius to point a subsequent straight section towards a central apex. Itis appreciated that any filter element profile may be used to positionthe filter element in a deflection reducing configuration to inherentlyreduce filter element strain.

Using Castiglianos theorem, the filter element deflection, δ_(F), isexpressed below.

$\delta_{F} = {\frac{F}{EI}\left\{ {{\int_{0}^{L}{{\left( {{L \cdot \cos}\; \gamma} \right) \cdot \left( {{L \cdot \cos}\; \gamma} \right)}{x}}} + {\int_{0}^{\beta}{{\left( {{{L \cdot \cos}\; \gamma} + {{r \cdot \sin}\; \beta}} \right) \cdot \left( {{{L \cdot \cos}\; \gamma} + {{r \cdot \sin}\; \beta}} \right)}{r \cdot \beta}}}} \right\}}$$\delta_{F} = {\frac{F}{EI}\left\{ {{\int_{0}^{L}{\left( {{L \cdot \cos}\; \gamma} \right)^{2}{x}}} + {\int_{0}^{\beta}{\left( {{{L^{2} \cdot \cos^{2}}\gamma} + {{2 \cdot L \cdot r \cdot \cos}\; {\gamma \cdot \sin}\; \beta} + {{r^{2} \cdot \sin^{2}}\beta}} \right){r \cdot {\beta}}}}} \right\}}$$\delta_{F} = {\frac{F}{EI}\left\{ {\frac{{L^{2} \cdot \cos^{2}}\gamma}{3} + {{r \cdot L^{2} \cdot \beta \cdot \cos^{2}}\gamma} - {{2 \cdot L \cdot r^{2}}\cos \; {\gamma cos\beta}} + \frac{r^{3}\beta}{2} - \frac{r^{3}\sin \; 2\beta}{4}} \right\}}$ε=My/EI=Mt/2EI, where the moment M=F·(L·cos γ+r·sin β)

then,

$ɛ = {3 \cdot \delta_{F} \cdot {t\left\lbrack \frac{{{L \cdot \cos}\; \gamma} + {{r \cdot \sin}\; \beta}}{\begin{matrix}{{2{L^{3} \cdot \cos^{2}}\gamma} + {6{L^{2} \cdot \cos^{2}}{\gamma \cdot r}} - {12{L \cdot}}} \\{{\cos \; {\gamma \cdot \cos}\; {\beta \cdot r^{2}}} + {2{r^{3} \cdot \beta}} - \frac{3{r^{3} \cdot \sin}\; 2\; \beta}{2}}\end{matrix}} \right\rbrack}}$

As the straight section of the filter element is tangential with theinitial radius, β=γ,

then,

$ɛ = {2 \cdot \delta_{F} \cdot {t\left\lbrack \frac{{{L \cdot \cos}\; \beta} + {{r \cdot \sin}\; \beta}}{\begin{matrix}{{2{L^{2} \cdot \cos^{2}}\beta} + {6{L^{2} \cdot \cos^{2}}{\beta \cdot r}} - {12{L \cdot}}} \\{{\cos^{2}{\beta \cdot r^{2}}} + {2{r^{2} \cdot \beta}} - \frac{3{r^{2} \cdot \sin}\; 2\beta}{2}}\end{matrix}} \right\rbrack}}$

In this example, the relationship between filter element length andstrain is more complicated with relations to the filter element arcangle β. These variables should be limited by balancing capture space(the volume of the capture cone increases with increasing filter elementlength) and parking space (parking space increases with increasingfilter element length) while fine tweaking to reduce strain. Similarlyto the prior art device, strain has a direct relationship withdeflection and filter element thickness. Filter element strain reduceswith decreasing filter element thickness; however, filter elementthickness should be kept high enough to contribute sufficient radialforce in order to prevent the device from migrating.

Unlike the prior art, deflection is determined by a combination ofvessel size and shape setting position. By shape setting the filterelements to have their ends positioned approximately one quarter of theway between the filter's central axis and the vessel wall (whenconstrained in the upper vessel size limit without the use of a holder),the deflection is reduced by approximately 75% when compared to theprior art device. The filter element deflection will also be halved forthe present invention when constrained in the lower vessel size althoughthe bending direction will be reversed as the filter elements will pressagainst each other rather than pull away from each other. The reductionin deflection will in turn reduce filter element strain significantly. Areduction in strain will significantly improve fatigue resistance in anenvironment where the filter experiences deflections at a rate of 70/minradially and 20/min longitudinally due to pulsatile blood flow andrespiration respectively.

In a preferred embodiment, the device of the present invention isindicated across a vessel size range, ideally from 16 mm to 32 mminternal diameter, and the filter elements are shape set to curveradially inwardly to a point that is slightly offset from a position onequarter of the way between the central axis and the vessel wall ifconstrained in the upper vessel size when a holder is not in place.Considerations in this embodiment include effects of the filter elementprofile centroid and material properties.

Referring to FIG. 10, the image on the left illustrates a typical crosssection of the filter element if it is cut from tubular stock, theunbroken line depicting the filter element cross section, and the brokenline depicting the tubular stock. The image to the right depicts thefilter element cross section with parametric designations. In order todetermine the offset orientation, the centroid must be calculated todetermine which bending direction will yield the highest strains. It isappreciated that the corners of the filter element profile may berounded.

Distance of centroid from O=Moment of area about y axis/area of thefigure

Area=r·dθ·dr,

Moment about y axis=r·dθ·dr·r·cos θ=r ²·cos θ·dr·dθ

Then,

${{Moment}\mspace{14mu} {of}\mspace{14mu} {area}} = {{\int_{- \alpha}^{\alpha}{\int_{r_{i}}^{r_{0}}{{r^{2} \cdot \cos}\; {\theta \cdot {\theta} \cdot {r}}}}} = \frac{2{\left( {r_{0}^{3} - r_{i}^{3}} \right) \cdot \sin}\; \alpha}{3}}$Area = ∫_(−α)^(α)∫_(r_(i))^(r₀)r ⋅ θ ⋅ r = (r₀² − r_(i)²) ⋅ α${{Distance}\mspace{14mu} C\mspace{14mu} {of}\mspace{14mu} {centroid}\mspace{14mu} {from}\mspace{14mu} O} = {\frac{2\sin \; \alpha}{3\alpha} - \frac{\left( {r_{0}^{2} - r_{i}^{2}} \right)}{\left( {r_{0}^{2} - r_{i}^{2}} \right)}}$

In order to determine which bending direction will yield the higheststrains, the centroid can be compared to a theoretical position of equalstrain. Referring to FIG. 11, the position of equal strain, “ES”, ishalf way between the position closest to the centre O and the positionfarthest from centre O.

Then,

ES = c + a/2${b = {\frac{r_{o}}{\cos \; \alpha} - r_{i}}},{a - {{b \cdot \cos}\; \alpha}},{a = {r_{o} - {{r_{i} \cdot \cos}\; \alpha}}},{c = {{r_{i} \cdot \cos}\; \alpha}}$${ES} = \frac{r_{o} + {{r_{i} \cdot \cos}\; \alpha}}{2}$

The arc angle of a single filter element=2α. The present invention maycomprise one or more filter element(s) and one or more connectorstrut(s) with a proximal and distal support hoop. The minimum number ofproximal and distal peaks of the proximal and distal support hoopsrequired to manufacture the filter is 2, due to geometry constraints.The maximum number of proximal and/or distal peaks required is 12; morethan this will reduce the radial force and increase delivery profilebeyond acceptable limits. Then, 2α should not exceed 60° where a filteris supplied comprising 2 proximal and distal peaks, 2 connector struts,and 4 filter elements as the number of struts to be cut radially fromthe tube will be 6. The angle 2α will reduce as connector and/or filterelement numbers increase. Therefore, ES can be compared to the distancefrom the centroid to point O for 2α≦60°. More preferably, the filtercomprises an array of 6 to 12 filter elements with 4 to 8 connectorstruts. Then, 2α will be <36°. It is appreciated that the actual anglemay be smaller as the cutting process will reduce the available degreesfrom the tubing. In addition, the connector elements may have widerstrut widths than the filter elements in order to balance the supportframe stiffness relative to the filter elements. This would also reduce2α.

In order to provide a filter with a low delivery profile, the raw tubingouter diameter should not exceed 8 mm and to provide sufficient radialforce and structural support, the OD should not be lower than 1.5 mm.The wall thickness of the tube contributes towards strut stiffness andto satisfy radial force and structural support requirements, the wallthickness should be greater than 0.15 mm. The wall thickness should notexceed 0.8 mm as this would increase radial force and/or deliveryprofile beyond acceptable limits. Then, the raw tubing O.D. should rangefrom 1.5 mm to 8.0 mm with a wall thickness ranging from 0.15 mm to 0.8mm. More preferably, the raw tubing O.D. should range from 2 mm to 6.0mm with a wall thickness ranging from 0.25 mm to 0.45 mm.

Therefore, preferred limitations are:

-   -   r_(o) ranges from 1.5 to 8.0 mm    -   wall thickness ranges from 0.15 to 0.60 mm    -   2α≦60°

ES≦Centroid and (Centroid−ES) increases with increasing 2α. Then, filterelement strain will be higher in compression when bending towards thecentre O than that for a filter element bending away from the centre O.Similarly, filter element strain will be higher in tension when bendingaway from the centre O than that for a filter element bending towardsthe centre O. A method of reducing tensile or compressive strain is toreduce the deflection in a particular bending direction.

Surface cracks that may be present are more likely to propagate undercyclic tensile strains than cyclic compressive strains. Then, it is moredesirable to balance tensile strains across the indicated vessel sizerange. Further, NiTi is stronger in compression than in tension. Then,it is preferred that the filter element be positioned in a way thatreduces tensile strains to improve fatigue resistance.

Considering a filter device indicated for a vessel size range from 16 to32 mm, the filter elements will have equal tensile strain in the upperand lower vessel sizes if the filter element ends are positioned at apoint radially outwardly of a quarter way position between the centralaxis and the support frame when constrained in the upper (largestindicated) vessel size (due to ES≦C). With reducing 2α, the filterelement ends offset position radially outwardly of the quarter wayposition also reduces. Similarly, the filter element ends will form acentral apex when positioned in a vessel that is smaller than the middlevessel (24 mm) of the 16−32 mm vessel size range.

In general, the filter elements have positions when unconnected suchthat the filter element ends are located between the support frame andthe central axis when the vascular filter device is unconstrained.

While the extent of the distance from the central axis is stated aboveas being preferably one quarter (25%) of the distance from the centralaxis to the support (radius), it could be in the range of 10% to 50% ofthis distance and more preferably in the range of 15% to 40%. Also, thisis the preferred filter end position when the device is constrained in avessel in the top third of the indicated size range the filter elementend.

When the device is constrained in a vessel at approximately the middleof the indicated size range (about 22 mm to 26 mm for the aboveindicated size range) the filter elements are within +/−10% of theradius from the central axis.

When the device is constrained in a vessel of the lower third of theindicated size range (about 16 mm to 22 mm for the above indicated sizerange) the filter elements are within about 15% to 40% of the radiusfrom the central axis, on the opposed side (see FIG. 6( b)).

It is appreciated that the filter element may have single straightstruts, single curved struts, or a combination of both. A preferredfilter element is of a V-shaped construction with a straight and/orcurved profile (refer to FIG. 7).

Shape set filter elements may also be supplied with a support frameconsisting of a proximal support hoop alone or with any other supportframe design.

The shape set filter arms form an apex without the use of a holder whenconstrained in a tube with an internal diameter radially outwardly ofthe middle (24 mm) of the vessel size range (16 to 32 mm).

The filter elements and the support may be heat set in a tubular shapein order to achieve minimum filter element strain in the crimpeddelivery configuration.

The filter device may be formed to have a diameter that is larger thanthe upper vessel size in order to afford sufficient radial force to thedevice. For instance, with an indicated vessel size range of 16 to 32mm, the unconstrained diameter may be 36 mm, or more preferably, 34 mm.The balance of filter element deflection should take into account theupper (32 mm) and lower (16 mm) vessel sizes and not the unconstrainedvessel size. It is appreciated that a narrower or broader vessel sizerange may be chosen. A preferred vessel size range is 16 to 28 mm.Depending on support frame design, the connection between the filterelements and support frame may be positioned up to 2 mm radiallyinwardly of the average vessel size. Offsets such as these should beaccounted for when balancing strain across the indicated vessel sizerange. Similarly, the support frame may taper, curve, flare, or undulatefrom the proximal to distal end. Again, when balancing the strain acrossthe indicated vessel size range, the distance between the filter elementconnection to the central axis in the upper and lower vessel sizesshould be taken as the filter element deflection range.

Any of a variety of means may be employed to secure the filter elementstogether at their ends to form the apex including holders disclosed inWO2010/082187. The following are further embodiments that can be used.Where shape set filter arms curve radially inwardly, the holder shouldbe manufactured of a biostable material.

FIG. 12, crimped together inside a tube 10.

FIG. 13, crimped within the tube 10 against an axial pin 11.

FIG. 14, crimped as in FIG. 13, except in this case the pin has a head13 to aid positioning of the pin during manufacturing.

FIG. 15, a tube 15 has an array of slots for each or a group of filterelements. The tube is crimped onto the filter elements from the ID tothe OD of the tube. Alternatively, the filter elements can be placed inan array of slots in a tube or rod and be coupled to the tube or rod bywelding, snap fitting, or by bending at least one of the capture armsdistal to the apex to prevent the coupling tube or rod from dislodging.Adhesives may also be used to fix the apex in place.

FIG. 16, a coupler 20 having an annular socket 21 may be used to receiveand crimp the filter element ends. The coupler may be open at both ends,as shown in the coupler 25 of this drawing.

FIG. 17, the filter elements may be twisted together or tied together ina “Teepee” arrangement.

FIGS. 18 and 19, the filter elements have interlocking features to holdthem together at the filter apex. The interlocking features may bemachined, bonded, or otherwise attached.

FIG. 18 shows filter elements 35 with grooves 36 on one side andinter-engaging ridges 37 on the opposed side. FIG. 19 shows filterelements 50 with opposed dovetail features 51 and 52, elements 55 withonly male dovetail ridges and elements 60 with only female dovetailslots, with the elements 55 and 60 interconnecting as illustrated inFIG. 10. Alternatively, snap fit features may be used to interlock thefilter element ends.

-   -   The designs shown in FIGS. 12 to 14 and the top of FIG. 16 offer        streamlined profiles when compared to pins and ties as they are        concentric with the apex and can be kept to a low profile (small        diameter). FIG. 15 and the bottom of FIG. 16 offer similar        advantages while also facilitating blood flow through a central        axis in order to minimise stagnant areas.    -   The interlocking features of FIGS. 18 to 19 offer a more        streamlined profile by providing minimal material at the apex        and facilitating blood flow through a central lumen.    -   A streamlined profile will reduce irregular flow patterns and        shear blood flow forces to in turn reduce fibrin and/or clot        formation.

These principles are also applicable to a filter where the ends of thefilter elements are integral. An integral filter element end presents anadditional challenge in that one cannot heat set the filter element endsto be positioned approximately one quarter way between the central axisand the vessel wall in the maximum indicated vessel size as the ends ofthe filter elements are not free—they are connected integrally. For suchcases, it is possible to heat set the support frame separately to thefilter portion thereby allowing the support frame to be biased to anunconstrained diameter of 34 mm (affording additional radial force forplacement in a max indicated vessel size of 32 mm) and the filterelements can be biased to have similar strain when constrained in theminimum and maximum indicated vessel sizes. This could be achieved byheat setting the complete implant for an unconstrained diameter of 34 mmand then insulating the support portion while heat setting the filterportion when constrained in a vessel approximately in the middle of thevessel size range. Alternatively, this could be achieved in reversewhere the implant is heat set in a vessel approximately in the middle ofthe vessel size range and then insulating the filter portion while heatsetting the frame to have an unconstrained diameter of 34 mm.

Integral Apex

In some embodiments a vascular filter device has a support structurewhich is preferably stent-like in overall configuration, and preferablyhas proximal and distal hoops linked by connecting struts. The devicepreferably has a filter with filter elements connected to the support atone end and converging at the other end. In some embodiments theyconverge at an apex. The area of convergence is integral with at leastsome of the filter elements.

For example, the apex may be integral with the filter elements alone,with the filter elements and a portion of the support frame, or with aportion of the filter elements. This is advantageous for fatigue andmanufacturing efficiency. The apex is the same diameter as the laser cuttube that the support frame and filter elements are cut from beforeexpansion to the desired in-use diameter. However, it introduces achallenge in keeping a distal crown arrangement as the connector strutsinherently split the integral filter apex into six separate filterelement ends. The embodiments provide means to include a proximal anddistal crown with an integral filter apex where the filter is cut fromthe raw tube in multiple pieces.

The filter is cut from the raw tube in two pieces, proximal and distal,preferably from the same tubing stock. This is shown in FIG. 20 in whicha device 201 has separate proximal and distal parts 202 and 203 cut fromthe same tube.

FIGS. 21 and 22 show the device in more detail. The proximal part 202has proximal peaks 205 of a proximal support hoop, distal peaks 206 ofthis hoop, filter elements 207 (or “capture arms”), proximal connectorstruts 208, a cylindrical filter apex 209 which is integral with thefilter elements. The distal part 203 has connectors 210, hoop proximalpeaks 211, and distal peaks 212

Once laser cut, the proximal and distal pieces are expanded to increasethe filter diameter, as shown in FIGS. 23 and 24. For delivery, theexpanded filter is crimped to a diameter closer to the raw tubingdiameter in order to transfer it into a catheter for low profiledelivery.

Once expanded, the distal and proximal pieces are connected together viawelding or mechanical means as shown in FIG. 25.

The proximal and distal pieces may alternatively be connected togetherbefore expansion.

In summary, the proximal piece 202 includes a proximal crown 205, 206,an array of filter elements 207 and an array of connecting struts 208.The distal piece 203 includes a distal crown 211, 212 and an array ofconnecting struts 210. The filter is joined by coupling the connectingstruts 208 and 210 from both proximal and distal pieces. The couplingmethods may include but are not limited to welding, crimping, swaging,adhesive bond, and/or snap fitting. The connection between proximal anddistal may be provided at any point along the connector struts proximalto the position of the filter apex. The connector strut is advantageousfor coupling the two pieces as it is a low strain region and will notimpact fatigue performance significantly.

A developed view of the tubular laser cut pattern (tubular view shown inFIGS. 20 to 22) for the proximal and distal halves is shown in FIG. 26to illustrate how the connector struts cannot extend past the integralapex. A developed view is an image of the tubular pattern rolled outflat. The drawing to the left depicts the proximal support hoop,proximal half of the connector struts, the filter elements and theintegral apex while the drawing to the right depicts the distal half ofthe connector struts and the distal support hoop. If the developed viewis rolled so that the top and bottom are joined, it depicts the tubularlaser cutting pattern used to machine the parts from a raw tube. Thelaser cut tube is then expanded to form the filter and heat set toremember its new shape. This is done by expanding the laser cut tubeinto its new shape and constraining in a fixture or on a mandrel andthen performing a heat treatment. The filter can then be crimped down toa diameter that is greater than, equal to, or less than that of the rawtube and loaded into a delivery sheath for low profile delivery to theimplant site. When deployed into an environment that is above the Aftemperature, the filter will revert to it's expanded form provided bythe shape setting step (for example, if the materials Af temperature is20 degrees Celsius, it will revert to its shape set form in anenvironment that is above 20 degrees Celsius such as that of blood at 37degrees Celsius. This step will reduce strains in the device whendeployed in a vessel. Alternatively, the device may be manufactured frommaterials with no shape memory properties such as spring steel or cobaltchromium in which case the device may be annealed to remove the stressesraised through work hardening.

As the integral apex is a tube that lies between the proximal and distalsupport hoops, it is not possible to include connector struts thatextend between the proximal and distal support hoops as they wouldinherently separate the integral apex into non-integrated apices. Thisis overcome by cutting proximal and distal segments separately andjoining them afterwards.

Referring to FIG. 27, the integral filter apex 209 has a smooth profilethat reduces disruption to blood flow and thus reduces thrombusformation by reducing stagnation and irregular blood flow patterns.Coupling means such as pins and ties can add complexity that may causeirregular blood flow patterns and/or stagnation leading to thrombusformation.

Referring to FIG. 28 a, alternatively, the connection point may beprovided at the proximal end of the filter elements. This device has aproximal part 250 with a proximal hoop and a filter, and a distal part255 with struts 256 and a hoop 257.

Referring to FIG. 28( b), in another embodiment, the array of filterelements 260 is provided separately to an integral support frame 261.

Further advantages of the separate filter portion is the ability toprovide a permanent filter or a permanent filter with the option toretrieve the filter portion should the need arise, leaving the supportframe behind. Refer to FIGS. 29 a to 31. For an optional filter with aseparate support frame, it is advantageous to provide a connectionbetween the support frame and filter that is low profile and streamlinedso that during retrieval, minimal trauma is caused to any neo-intimal. Apreferred solution comprises a filter portion with an array of pinshaped proximal ends. During retrieval, the apex of the filter isengaged from a jugular approach and pulled cranially into a sheath toslide the pin shaped proximal filter element ends through endothelialgrowth. The attachment means between the filter and support frame mayinclude a bond, interference fit, breakable component, crimpedcomponent, heat shrink, magnet, tie or other mechanism that requires apredefined force to release the filter—this will ensure the filter isnot released inadvertently if the release force was too low and willprevent damage to the vessel wall if the release force was too high.Ideally, the release force would range between 3 N and 15 N, morepreferably between 5 N and 10 N.

FIG. 29( a) shows a support 280 and FIG. 29( b) shows a separate filter290, and FIG. 30 shows the completed device after interconnection.

Referring to FIG. 31, this shows how the supports 280 and 290 areinterconnected within a sleeve 310.

The distal crown may be provided as a single piece given that the filterelements are longer than the connector elements from the point where thefilter elements meet the connector elements. This is advantageousbecause a shorter filter can be manufactured. A shorter filter can alsobe achieved with short connector elements on both proximal and distalpieces. This is shown in FIG. 32, in which a proximal part 350 connectswith a distal part 360 comprising only a hoop.

Alternatively, the connection point may be provided along the filterelements as this too is a low strain region. FIG. 33 shows such a firstpart 400 and second part 410.

Welds used to join the laser cut parts may include but are not limitedto the weld types (welds depicted as filled in areas) shown in FIG. 34.These include butt and overlap joints, some with profiling ends.

Dovetail like features may be used to interlock struts. These featuresmay be combined with welding, adhesive bonds, and/or crimping, as shownin FIG. 35.

A ball and socket joint 450 could be formed on the connectors to providea flexible connection (FIG. 36).

The ball and socket features could be manufactured separately andattached as parts 500 and 501 in FIG. 37. Any form of hinge may be usedto increase flexibility of the attachment.

Crimping tubes 510, 515, and 520 may be used to join struts. Ridge orrecess features may be provided on the struts, crimping tube, or both toincrease the strength of the joint (FIG. 38) Struts 530 may be machinedto provide a slot and tie arrangement. The tie may be formed into a hookshape through mechanical or heat setting methods (FIG. 39).

Snap fit features 540 may be laser cut on the connector struts to lockinto an array of snap fit receptors (FIG. 40). The snap fit receptorsmay be biodegradable so that they separate after a predetermined periodof time.

A biostable thread or biodegradable filament 550 may also be used toattach proximal and distal connector struts (FIG. 41). Each connectorstrut may have an opening or feature that the thread or biodegradablefilament can be threaded through.

When a filter with an integral apex is crimped for the deliveryconfiguration, the delivery profile is governed by the wall thickness ofthe connector struts and the OD of the filter apex. The apex may beformed to provide a recess for each connector strut. This may beachieved by crimping the filter apex or by machining the filter apex.This is shown in an apex arrangement 560 in FIG. 42.

The proximal and distal connector struts connected by a thread orbiodegradable filament may be spaced apart so that the apex lies betweenthem when in the delivery configuration.

The raw tube, from which the proximal filter portion is cut, may beformed to have a necked down region 570 at the distal end to provide anintegrated apex with a smaller OD than that of the proximal and distalsupport crowns (FIG. 43).

In another embodiment the apex may be connected to a distal support,FIG. 44. The filter comprises a proximal support crown 600 with an arrayof short connector elements 601 extending from each distal peak of theproximal crown. Two curved filter elements (possible to include 1, 2, 3,or more filter elements) extend from the distal end of each connectorstrut 401 to an integral tubular shaped filter apex 602. Two distalsupport struts extend distally from the filter apex to a distal supportcrown. It is possible to include 1, 2, 3, or more distal support struts.Fewer distal supports are preferred in order to minimise disruption tothe blood flow. However, a balance is required between stability andflow obstruction where an increase in number of distal support strutsenhances stability.

As shown in the device 620 of FIG. 45, it is possible to enhance vesselcontact by extending the connector struts distally to a point proximalof the filter apex. Additional distal connector struts may extendproximally from the proximal peaks of the distal support crown.

Further modifications can be made to include V-shaped support elements625 extending proximally along the vessel wall from the distal crownand/or distally from the proximal crown (FIG. 46).

An integral filter apex 630 (FIG. 47) provides flexibility between theproximal and distal support crowns.

Referring to FIG. 48, a C-shaped integral filter apex is provided whereone (or more) connector element(s) 651 in a device 650 is cut through afully integral tubular filter apex to form a C-shaped filter apex 651.This allows for an integral filter device with a proximal support crown,a distal support crown, a connector strut connecting the proximal anddistal support crowns and a filter portion connected to the supportframe between the proximal and distal support crowns.

As shown in FIG. 49, vessel wall contact can be enhanced by extendingstruts 670 distally from the proximal support crown and/or by extendingstruts or v-shaped elements proximally from the distal support crown.

The C-shape integral filter apex can be modified to cut two or moreconnector struts 680, 681 provided means are provided to join the filterapex. Where two connector struts are cut, the filter apex can be joinedsimply with a pin, ring or weld. FIG. 50 shows elevation view of thefilter with two connector struts.

The C-shape integrated apex with two connector struts cut from it at 180degrees to each other may not require fastening to form the filter shapeas the 6 filter struts connected to each half would provide sufficientforce to prevent the apex from moving significantly radially upon impactof a blood clot or through movement of the vasculature. However, the twopiece apex can be joined using fasteners such as a pin, ring, crimpingmethods, swaging, or weld. This is shown in FIG. 51. Alternatively,magnets could be supplied on each half to keep them together.

Referring to FIG. 52, inclusion of 4 connector struts with a C-shapeintegrated apex yields 4 separated apex portions, that when assembledtogether; provide a smaller apex tube OD than the original cut tube OD.This is advantageous to achieve a low profile in the crimped deliveryconfiguration. When crimped, the connector struts must lie across the ODof the apex, thereby, increasing the overall OD of the apex. A reducedapex OD will in turn allow the crimped delivery configuration to have alower profile. Once assembled the 4 apex portions can be coupled using avariety of methods including but not limited to welding, low profileties, caps, pins, magnetism, and rings. It is appreciated that some ofthese coupling means may increase the OD of the apex, however, weldscould be applied in and/or outside the tubular apex and be ground downto remove excess material. Pins could be positioned so that the pinheads are misaligned with the connector struts and caps or rings couldbe profiled to provide a reception space for the connector struts.

Mating features 690 (FIG. 53) can be included to enhance the differentcoupling means while simultaneously imparting flexibility in theconnector struts to allow for more conformability of the implant in thevessel (i.e. for curved vena cavae). The top left and right images showthe filter apex before and after assembly respectively and the bottomimage shows the connector strut.

Referring to FIGS. 54 to 55, it is possible to machine and/or shapeflexible features for the connector struts, such as a sine wave 691, anoffset sine wave 692, M-shaped 693, W-shaped 694, nested 695, elongated696, or coil-shaped articulations 697.

It is also possible to provide flexible features in differentconfigurations over the length of the filter. They may be placed on thecentre of each connector strut (698 a, FIG. 56( a)), or a number ofarticulations 698 b placed on each connector strut (FIG. 56( b)). Thearticulations may be equally distributed along the length of theconnector or grouped together.

Further articulation embodiments are as follows, with reference to FIG.57:

-   -   698 c, Spiral pattern of articulations to produce a spring-like        flexibility in the frame,    -   698 d, X-shaped distribution to allow greater bending in the        plane shown, or    -   698 e, Articulations may also be provided at joints to crowns.

Integral Filter Device

In some embodiments, a filter apex is integral with the filter elementsthat are in turn integral with a longitudinal support structure. Thelongitudinal support structure eliminates tilting once sufficient lengthis afforded to it, for example, if the device length is a multiple ofthe diameter of the vena cava in which it is implanted. A balancebetween implant length and tilting must be provided to ensure thatimplant length is kept to a minimum. When deployed in the filtersmaximum indicated vessel size, the ratio of filter length to vesseldiameter should range from 1:1 to 2.3:1. More preferably, the ratio offilter length to vessel diameter should range from 1.5:1 to 2:1. Thelongitudinal support is designed to press against the vessel wall withsufficient radial force to prevent migration in the vessel. The supportmay also be fitted with barbs or protrusions to aid in anchoring it tothe vessel wall. The filter elements connect to the apex in a way thatminimises obstruction to the blood flow, for instance, it is preferredthat two or more filter elements merge into one filter element in closeproximity to the apex in order to provide a streamlined connection(refer to FIG. 62). The proximity of the merging point to the apexshould range from 1 to 10 mm; a range of 3 to 6 mm is preferred.

Referring to FIG. 58, a filter device 701 has a filter 702 which isconnected at the distal end of the device 701 to a distal support hoop703. Because the filter 702 extends from one end of the support it maybe integrally manufactured from a tube by laser cutting in one piece.The filter elements may be attached to the hoop (703, FIG. 58) or toextended connector elements (712, FIG. 58). Alternatively, the pluralityof connector elements may extend from the struts or distal peaks of thedistal support hoop.

FIG. 59 shows on top the filter device 710 oriented in the oppositedirection. This device may be improved by inverting the filter to pointinto the space encompassed by the support, as shown by a filter 721 in adevice 720 in the bottom of FIG. 59. The filter may be connected to theproximal support hoop or proximal to the proximal support hoop with theaddition of proximal connecting struts. The device is cut from a tubeand expanded with the apex facing proximally. In order to keep capturedclots central in the blood flow, the filter apex is directed distallythrough inversion of the filter inside the tubular support structure.Heat setting techniques may be employed to reduce the risk of the filterrighting itself back outside of the tubular support. The filter's innershape may change from a concave parabola to a convex parabola orintermediate configurations.

Referring to FIG. 60, alternatively, the tubular support structure canbe inverted over the filter cone to change a device 710 to a device 730as illustrated. This approach keeps the filter cone shape as a concaveparabola.

Referring to FIG. 61 a device 760 has a proximal hoop 761, connectorstruts 762, a filter 766 and a distal support hoop 763. The distalsupport hoop 763 comprises an array of V-shaped distal supports 766 andextension struts 764 in which the array of extension struts areconnected to the connector struts. Alternatively, the extension strutsmay be omitted if the array of v-shaped distal supports is connected tothe connector struts. Elevation and end views are shown at the top ofFIG. 61 with a plan view in the middle and a projected view below. Thefilter elements 765 extend to a central apex at a point distal to thedistal peak of the distal hoop when in the laser cut unexpanded stateduring manufacturing. Each distal support hoop comprises extensionsupport struts 64 that extend beyond the point of connection between thefilter elements and the support structure. The extensions are connectedto an array of v-shaped struts 766 that provide a radial force to keepthem pressed against the vessel wall. The device has two extensionstruts 764 for every proximal connector strut. A disadvantage of thedistal filter 701 and 710 is that it adds length to the device for agiven tubular length (ie length from proximal peak of proximal hoop todistal peak of distal hoop). The integral filter design of device 760 isadvantageous as it allows for a shorter filter length and thus improvedimplant length with a reduced length of vena cava required as a suitablelocation for implanting the device. The filter apex may move closer toor inside the tubular support structure when it is deployed in a vesseldue to foreshortening upon expansion. Foreshortening is the reduction inlength of an expandable device as it moves from a compacted deliveryconfiguration to an expanded configuration in use. As the deviceexpands, the v-shaped supports, that afford radial force to the device,move from an acute v-shape in the compacted delivery configuration to anobtuse v-shape in the expanded configuration during use. The more obtusethe v-shape for a given strut length, the greater the reduction in axiallength. Two or more filter elements may merge into one filter element inclose proximity to the apex in order to provide a more streamlinedprofile to minimise obstruction to the blood flow. This will reduceirregular flow patterns and shear blood flow forces to in turn reducefibrin and/or clot formation. Refer to FIG. 62 illustrating the y-shapedfilter elements 766 and apex 767.

A developed pattern is shown in FIG. 63 that could be used to laser cutthe device from tubing stock. If the developed view is rolled so thatthe top and bottom are joined, it depicts the tubular laser cuttingpattern used to machine the parts from a raw tube. The laser cut tube isthen expanded to form the filter. If the filter is made from Nitinol ora similar material with shape memory properties, the expanded filter canbe heat set to remember its new shape. This is done by expanding thelaser cut tube into its new shape and constraining it in a fixture or ona mandrel and then performing a heat treatment. The filter can then becrimped down to a diameter that is greater than, equal to, or less thanthat of the raw tube and loaded into a delivery sheath for low profiledelivery to the implant site. When deployed into an environment that isabove the Af temperature, the filter will revert to it's expanded formprovided by the shape setting step. For example, if the materials Aftemperature is 20 degrees Celsius, it will revert to its shape set formin an environment that is above 20 degrees Celsius such as that of bloodat 37 degrees Celsius.

Alternatively, if the device is formed from other materials with noshape setting properties such as spring steel or cobalt chromium, theexpanded device may be annealed to remove the stresses raised throughwork hardening.

It is also possible to connect the extension support struts and/orfilter elements to the proximal support hoop.

Referring to FIG. 64 a device 780 has a proximal hoop 781, connectorstruts 782, a distal hoop array 783, and a filter 785. In thisarrangement the filter has been shortened by adjusting the proximalconnector and/or extension support strut length. The distal hoop arraycan also be flared to aid vessel wall apposition, deployment accuracy,and resistance to migration. A distal flare is a section at the distalend where the cylindrical profile tapers outwardly to form a largerdiameter than the cylindrical profile, refer to FIG. 64. Similarly, theproximal hoop may also be flared to further assist vessel wallapposition, deployment accuracy, and resistance to migration. In anotherembodiment, the proximal and/or distal hoop flares may extend across theproximal connector struts and/or extension struts. The support structureshould be at least as long as the diameter of the largest indicatedvessel diameter, preferably, the ratio of the support structure lengthto the diameter of the largest indicated vessel should be in the rangeof 1:1 to 2.3:1, more preferably 1.5:1 to 2:1, in order to preventtilting. In the case of the short filter with equal length and diameter,the flared distal support array will aid tilt prevention.

Referring to FIG. 65 the extension struts may be connected to theproximal hoop, the proximal connector struts, or the filter elements.The filter elements may be connected to extended connector struts,extension struts, the proximal hoop, or the connector struts. It is alsopossible to omit the proximal connector struts by connecting the filterelements or extension struts to the proximal hoop. An extended connectorstrut may also be provided; this would reduce the number of filterelement connections at the vessel wall as the extended proximalconnector strut would bend radially inwards to a point away from thevessel wall before splitting into two or more filter elements. Lessfilter element connections at the vessel wall will provide a morestreamlined profile to minimise areas of stagnation, reduce irregularflow patterns and shear blood flow forces to in turn reduce fibrinand/or clot formation. Alternatively, one filter element may be providedfor every proximal connector strut or one filter element may be providedfor every second proximal connector strut.

Referring to FIG. 66 in a device 810 an integral filter apex 815 can bepositioned proximal to the distal peak of the distal support hoop 813provided that the position of the apex 815 is positioned close to thedistal tip of distal support hoop. This is possible as the axial lengthof the filter elements 816 reduces relative to the axial length of thedevice when the support structure 811, 812, 813, 814 is expanded from alaser cut tube (i.e. axial length of filter elements is less than filterelement length in the expanded configuration). This is due to the changein axial length of the filter element when moving from an unexpandedstate to an expanded state. FIG. 67 shows an expanded view of such adevice on top with two unexpanded developed views below. The devicecomprises a proximal support hoop 811 and an array of proximal connectorstruts 812, extension struts 814, distal v-shaped supports 813, filterelements 816, and an integral filter apex 815. The apex 815, being inclose position to the distal tip of the distal array of v-shapedsupports 813 when in the unexpanded position, moves to a point justproximal of the distal tip of the distal array of v-shaped supports 813.The broken lines depict the change in length of the filter element whenmoving from an unexpanded position to an expanded position.

Referring to FIG. 68, alternatively, filter elements 820 can be formedor heat set to have a reduced length in the expanded state than theirlength in the laser cut tube pre expansion. The top image depicts thefilter element pre forming while the bottom image depicts the filterelement shape set to have a reduced length. The reduced filter elementlength will position the filter apex more proximally inside the tubularsupport frame. The example shown includes a wave pattern with reducingamplitude from the proximal (left) end to the distal (right) end. Thishas an additional advantage in that it will improve capture efficiencycloser to the vessel wall where the plurality of filter elements arespaced wider apart than at the apex where the plurality of filterelements merge together. It is appreciated that any shape apart fromstraight will reduce filter element length. Referring to FIG. 69, it isalso possible before expansion, to laser cut the connector struts 825with a lengthening pattern. Also shown are the struts 826 of theproximal support hoop, extension struts 827 and filter elements 828.Then, the connector struts can be pulled axially between the proximaland distal ends to lengthen them before heat setting. This will have theeffect of positioning the filter apex more proximally inside the tubularsupport frame.

Referring to FIG. 70 there is a device 830 with a proximal hoop 831,mirrored V-shaped struts 832, a distal hoop array 833, filter elements834, and an integral filter apex 835. The distal hoop has an array ofV-shaped segments 837 connected to the proximal support hoop throughconnector struts 836. The number of peaks for the distal hoop array 833can vary from 3 to 15 depending on the radial force required. Theexample 830 has a proximal support hoop with 12 proximal peaks whereevery second V-shaped segment has a mirrored V-shape segment extendingdistally. The mirrored V-shaped segment may be connected directly to theproximal support hoop or along the connector struts 836 of the distalsupport hoop. Singular filter elements extend distally from the distalpeak of the mirrored v-shaped segments to provide 6 filter elements intotal. Where fewer peaks are utilised, it is possible to increase thenumber of filter elements extending from the mirrored V-shaped segmentseither singularly or in groups. The filter elements can be shaped toprovide uniform filtration pores. An integral filter apex 835 isprovided by alternating between v-shaped struts 832 and v-shaped struts837. This feature provides the distal hoop array and allows the filterelements 834 to extend past the distal peak of the distal hoop array833. The filter elements meet the integral apex at a point just distalof the distal peaks of the disconnected distal support hoop when in thelaser cut unexpanded state during manufacturing. The integral filterapex may move to a point proximal of the distal peak of the distal hooparray when in the expanded state in use. The integral apex may beprovided more distally to the distal peaks of the distal hoop array inorder to provide a filter that extends past the distal peaks of thedistal support. This may be advantageous if the filter was deployed sothat the renal veins flow across the filter unobstructed by the supportstructure. The additional flow inlets at the renal veins would enhancelysis of any clot that was captured. Refer to FIG. 77 that shows theposition of the renal veins.

Referring to FIG. 71, in a device 840 with a proximal hoop 841, a distalhoop array 842, mirrored V-shaped struts 844, a filter 843 and integralapex 845 it is also possible to include mirrored V-shaped struts 846between the array of mirrored v-shaped struts 844 to provide a morebalanced radial force from the proximal region. This will aid in keepinguniform spacing between the array of connector struts 847 to provideuniform filtration pores when in use in the expanded state.

Referring to FIG. 72 a device 850 has a proximal hoop 851, filterelements 852 and paddle supports 855 comprising connector struts 853 anddiamond shaped elements 854. The connector struts extend distally fromevery second distal peak of the proximal hoop and filter elementsextending distally from every other distal peak of the proximal hoop.Each connector element may have a diamond, fork, or circular shapedfeature at the distal end to aid deployment accuracy, anti-tilting andresistance to migration. A closed cell shape such as a circle or diamondis advantageous in resistance to perforation because there are nounattached or uncoupled struts that might perforate the vessel. Thefilter elements and connector struts may be connected to other parts ofthe proximal hoop provided that they are supplied in an alternatingfashion.

It is appreciated that the devices of any embodiment can have distaland/or proximal flares to aid in preventing tilting and migration.

Referring to FIG. 73 a device 860 has a proximal hoop 861, a filter 862,connector struts 863, and a distal hoop 864. The distal supports can bejoined together by M-shaped elements extending from each connectorstrut. Where the connector struts attach to the centre of the M-shapedelements, adjacent M-shaped elements can be coupled together by welding,crimping, fastening or other means. This has the advantage of providinga continuous distal support hoop with the integral filter apex.

Referring to FIG. 74 it is also possible to provide more than oneannular ring at the proximal and/or distal hoops. The device, 870, shownhere has a proximal hoop 871, a filter 874, connector struts 872, and adistal hoop 873.

FIG. 75 shows an integral filter device 900 showing plan, elevation andend view with a proximal hoop 901, connector struts 902, distal v-shapedsupport struts 903, Y-shaped filter elements 904, and an integral apex905. Each of the filter elements 904 may be supplied as two singlefilter elements, one V-shaped filter element or one Y-shaped filterelement as shown. FIG. 76 a illustrates an oblique view of the deviceand FIG. 76 b illustrates a developed view of the device. The filterelements extend from the connector struts to an integral apex at a pointdistal to the distal peak of the distal V-shaped support struts. Theconnector struts 902 may have a distal flare at the connection of thefilter element as shown in FIG. 75 and FIG. 76 a. The flare may also beinitiated proximal to or distal to the filter element connection. Therepeating pattern has one Y-shaped filter element alternating with onedistal v-shaped support as shown in FIG. 76 b. Ideally, this pattern isrepeated 3 times but it is appreciated that less or more repetitions arepossible. More repetitions will result in more filter elements but willhave less radial force. Additional filter elements can also be providedby extending struts proximally from the integral apex between adjacentfilter elements 904. The proximal ends of the additional filter elementsmay be free ended or connected to adjacent filter elements 904,connector struts 902 or v-shaped distal supports 903. The filter elementextensions may be connected singularly or through v-shaped connections.Additional filter element extensions will provide reduced filter poresize for a given number of repeating patterns as discussed.Alternatively, a number of filter elements can extend between theintegral filter apex and the proximal support hoop 901, the connectorstruts 902, and/or the v-shaped elements 903. Referring to FIG. 76 c, inanother embodiment, distally pointing V-shaped filter elements 906extend between adjacent Y-shaped filter elements 904. This would reducefilter pore size and add a radial force to the filter element where av-shaped strut is provided. Alternatively, the V-shaped filter elements906 may point proximally. It is appreciated that filter elements can bereshaped through heat setting during or after expansion of the device inorder to provide a more uniform filter pore size.

FIG. 78 shows an integral filter device 950 showing plan, elevation andend views with a proximal support hoop 951, filter elements 952, andpaddle supports 953 comprising twin connector struts 954 and diamondshaped elements 955. The twin connector struts extend distally fromevery second distal peak of the proximal hoop with filter elementsextending distally from every other distal peak of the proximal hoop.The proximal and distal ends of the twin connector struts are notconnected together having the effect of splitting the proximal supporthoop into an array of M-shaped supports and opening the proximal ends ofthe diamond shaped elements. Each paddle support may have a diamond,fork, or circular shaped feature at the distal end to aid deploymentaccuracy, anti-tilting and resistance to migration. A closed cell shapesuch as a circle or diamond is advantageous in resistance to perforationbecause there are no unattached or uncoupled struts that might perforatethe vessel. The filter elements and connector struts may be connected toother parts of the proximal hoop provided that they are supplied in analternating fashion. Alternatively, the twin connector struts may beconnected at the proximal and distal ends to form an opening between theconnector struts. The twin connector struts may not be close together orparallel as shown.

In another embodiment, referring to FIG. 79, an integral filter device960 is illustrated showing plan, elevation and end views with proximalsupport paddles 963, filter elements 962, and distal support hoop 961.Paddle supports 963, comprising twin connector struts 964 and diamondshaped elements 965, extend proximally from every second proximal peakof the distal support hoop with filter elements extending distally fromthe proximal peak of the diamond shaped elements. The proximal anddistal ends of the twin connector struts are not connected togetherhaving the effect of splitting the distal support hoop into an array ofm-shaped supports and opening the diamond shaped elements. Each paddlesupport may have a diamond, fork, or circular shaped feature at theproximal end to aid deployment accuracy, anti-tilting and resistance tomigration. A cell shape such as a circle or diamond is advantageous inresistance to perforation because there are no unattached or uncoupledstruts that might perforate the vessel. The number of proximal anddistal peaks of the distal support hoop may be reduced while increasingthe number of proximal paddle supports and filter elements in order toreduce filter pore size. For example, if the number of distal peaks ofthe distal support hoop is halved, it is possible to double the numberof proximal paddle supports and filter elements. Then, the twinconnectors would split the distal support hoop into an array of distallypointing v-shaped supports. The twin connectors do not have to be closetogether or parallel as shown, it is possible to extend them at anglesor through curves along the tubular profile of the device. Proximaland/or distal flares may be included to aid deployment accuracy andresistance to migration. Alternatively, the filter elements andconnector struts may be connected to other parts of the paddle supports.In another embodiment, more than one filter element extends from eachpaddle support. In a further embodiment, the filter is connected to thedistal peaks of the distal support hoop and extends distally.

Referring to FIGS. 80 to 139, further holder embodiments are shown thatmay be employed to secure the filter elements together at their ends toform an apex—refer also to FIGS. 12 to 19. The holders are configured tosecurely hold the filter elements while reducing overall profile inorder to reduce obstruction to blood flow and aid in preventing thrombusformation and/or fibrin growth. These benefits are achieved whether theholder is used with a filter as described above or with a filter of theprior art which terminates in an apex. Also, they may be used withdevices of the type in which the filter remains permanently closed, orof the type which opens after a time such as when the holderbiodegrades.

FIGS. 80 to 85 depict holders in the form of an overlapping coil orspiral to allow them to be trained through eyelets of the filter elementends and to automatically fasten. It is the type of fastener known as a“cinch” or “key ring” type fastener. The holders are preferablymanufactured from wire or tubing that can be threaded through each of aplurality of circumferentially spaced filter element openings.

The drawings show spiral holders with overlapping wire in the axialdirection, and some also partly in the radial direction (for exampleFIG. 82). However, in other embodiments the wire overlaps in a single(radial) plane in the form of a planar spiral holder. In all spiralholder embodiments the wire may be trained through the filter elementend eyelets, the holder forming an integral fastener due to contact ofjuxtaposed spiral turns.

FIG. 80 and shows a holder 1000 with a wire 1001 coiled to overlap byabout 50% of a turn. FIG. 81( a) shows a holder 1005 which overlapsabout 110%. The diameter of the holder in FIG. 81( a) tapers radiallyoutwardly from the proximal end to the distal end while the holder inFIG. 80 has a constant outer diameter. The tapered diameter conformsbetter to the profile of the eyelets 1011 as shown in FIGS. 81( b) and81(c).

FIG. 82 shows a holder 1050 with 6 overlaps. FIGS. 83 and 84 showholders 1060 and 1065 with only a half coil overlap, and tapered ends ofthe wire to guide training through the eyelets.

The filter element openings can be machined during laser cutting of thedevice from raw tubing. To form circumferentially spaced openings withan integral support member, filter elements and filter element openings,the ends of the filter elements should be twisted approximately 90degrees (the filter element openings will face radially outwardly afterlaser cutting). Alternatively, filter element openings may be attachedto the ends of filter elements.

Preferably, the holder is provided with between 1 and 3 revolutions,more preferably with between 1.2 and 1.8 revolutions, and even morepreferably with between 1.4 and 1.6 revolutions. Additional revolutionsenhance the security of the cinch preventing the filter element endsfrom working their way back out of the taurus formed by the cinch.However, excessive revolutions may over-crowd the filter elementopenings thereby requiring a reduction in the circular/rectangular crosssectional area of the wire/tube that the cinch is formed from in orderto fit within a set filter element opening size.

It is preferred that the filter element opening or eyelet is kept smallto avoid the need to cut the filter from a larger diameter tube and/orincrease the compressed delivery profile of the device. Further, thecoiled holder with multiple revolutions will extend through each filterelement opening multiple times thereby increasing the complexity ofassembly. One or more of the eyelets may include a larger opening toaccommodate additional revolutions of holder, for example, where aholder is provided with 1.5 revolutions, the holder will extend oncethrough some of the eyelets and twice through other eyelets. The holdermay have a constant diameter at its proximal and distal ends or it maytaper radially outwardly from its distal end to its proximal end.

Tapering is advantageous in that the holder will not be strained duringuse due to the filter elements moving from the compressed deliveryprofile to the expanded delivery profile as the circumferential spaceformed by the filter element openings changes from having asubstantially constant diameter to having a diameter tapering radiallyoutwardly from the distal end to the proximal end. Alternatively, thecross sectional shape of the holder (circular or rectangular or other)may be reduced to afford additional flexibility to the cinch allowing itto conform to the changing space determined by the filter elementopenings when moving from the compressed delivery profile to theexpanded in use profile. For cinches cut from raw tubing, it is moredifficult to polish the surface of the cinch that resides betweenoverlapping revolutions. This can be aided by increasing the pitch ofthe revolutions to provide additional space between overlappingrevolutions allowing more efficient electro polishing. If it is desiredthat the space between overlapping revolutions is kept to a minimum formore stability, one of the free ends of the holder provided with anincreased pitch may be pulled over the other free end of the cinch afterpolishing so that overlapping revolutions press against each other andeliminate the space between them. If it is desired that this holder'scross section revolves clockwise from one end to the other, the holdershould be manufactured with an anti-clockwise revolution so that afterpulling one free end over the other to eliminate the space betweenoverlapping revolutions, the holder changes from revolvinganti-clockwise to clockwise.

In more detail, FIG. 80 shows a holder 1000 with constant diameter and1.6 revolutions, formed from wire. FIGS. 81( a) to 81(c) show a holder1005 formed from wire with a tapered diameter and 2.2 revolutions. FIG.81( b) shows the cinch 1005 assembled with six filter elements, five ofthe filter elements have a short opening and one of the filter elementshas a long opening as shown in the cross section images in the top andbottom of FIG. 81( c) respectively. Note how the tapered profile of thefilter elements matches the tapered profile of the holder 1005. As thetapered profile of the filter elements will vary between the minimum andmaximum indicated vessel sizes, the tapered profile of the holder ispreferably matched to the tapered profile of the filter elements whenconstrained in a middle vessel size of the indicated vessel sizerange—this will minimise wear and enhance durability across the fullvessel size range.

FIG. 82 shows another holder 1050 manufactured from wire with 5.25revolutions and a tapered diameter. FIG. 83 shows a holder 1060 cut fromraw tubing with 1.45 clockwise revolutions, minimal space betweenoverlapping revolutions, and tapered ends to aid easy threading througheyelets. FIG. 84 shows a holder 1065 cut from raw tubing with 1.45anti-clockwise revolutions, tapered ends, constant diameter, and withample space between overlapping revolutions to aid electropolishing—when one free end of the holder is pulled over the other, thisholder will resemble the holder shown in FIG. 83. FIG. 85 shows a holder1070 with 0.9 revolutions that has no overlapping revolutions andtherefore forms a taurus with constant cross sectional area.

Holders can be manufactured by laser cutting from raw tubing or byforming a length of wire. If made from shape memory material such asNitinol, the holder can be shape set or alternatively if made from wirewithout shape memory properties, can be annealed after forming to reducestresses in the component. The component may also be moulded using avariety of polymer materials.

Referring to FIGS. 86 and 87, clasp holders 1080 and 1090 are shown inwhich a wire is looped at one end and forms a hook at the other end sothat the hook features extend through the loop after threading throughthe filter element openings to secure in place. These embodiments ensurethat the holder wire extends twice through each filter element openingin order to afford additional security should one of the wires fractureduring use. Alternatively, the clasp holder 1080 may be provided withonly one or with multiple lengths of wire that extend through the filterelement openings. The clasp holder may be manufactured by forming shapememory material using a forming tool and heated to set the definedshape. Alternatively, the wire may be mechanically deformed into shapeand annealed after to reduce stresses. A flexible biostable orbiodegradable filament may also be used having a loop at one end asdepicted in FIGS. 86 and 87 where in place of a hook at the other end, aknot is tied, preferably a stopper knot. Alternatively, the filamentsmay be welded together in a manner that moulds a larger cross sectionthan the eyelet openings to prevent passage there through. The weldedend may pass through one of the eyelets more than once where it iswelded into an increased cross sectional profile or where a knot is tiedin order to form a loop around said eyelet to form an anchor point. Thiswould prevent the filament from becoming an embolus if the filament werebiodegradable as the filament would be attached to said eyelet and moveto the vessel wall with the eyelet after degradation (for convertiblefilter embodiment incorporating such a holder design).

FIG. 88 depicts a split ring holder 1100 with opposing saw toothsurfaces 1101 and 1102 that inter-engage when the ring is compressedafter threading through filter element openings to secure in place. Thisembodiment may be manufactured using laser or waterjet cutting machines.Alternatively, the holder may be injection moulded. The ring may also beheat set or annealed in its in use closed configuration so that it mustbe pulled apart in order to assemble with the filter elements. This willreduce the stresses during use as the member will be in its biasedstate.

FIGS. 89 to 93 show integral band holders in which a free end of a bandis threaded through filter element openings before being threaded backthrough the other end of the band where features exist to lock theholder in place.

In FIGS. 89 and 90 a holder 1120 has a male connector tab 1123 at oneend of a strip 1121 and a female connector tab 1122 with an eyelet 1124at the other end.

In FIG. 91 a holder 1140 has a male end 1141 extending from a strip 1142and a female end 1143 with a U-shaped eyelet 1144 in which one branch isshorter than the other.

In FIG. 92 a holder 1160 has a male end 1161 extending from a strip 1162and a female end 1163 with a an eyelet 1164 having openings linked by abridge.

In FIG. 93 a holder 1180 has a male end 1181 extending from a strip 1182and a female end 1183 with a slot 1184 extending at an angle to the axisof the strip 1182.

These embodiments may be laser cut from raw tubing, moulded, stampedfrom sheet metal or otherwise machined. FIG. 93 shows a belt-like holderin which one end is slotted into the other end offering a lower profilethan the variations shown in FIGS. 89 to 92 which will reduceobstruction to blood flow and aid in preventing thrombus formationand/or fibrin growth. Additional members may be attached to the band inorder to provide the loop and lock features.

FIGS. 94 to 97 depict a tubular holder 1200 with arms 1202 extendingfrom a ring-shaped base 1201 towards a central apex. Each arm 1202extends through a filter element opening 1206 providing security in theevent that should one holding arm fracture, only one filter element willbe affected. The holder 1200 may be laser cut from raw tubing and thenheat set with the arms extending towards a central axis. FIG. 94 showsthe holder 1200 post laser cutting while FIG. 95 shows it post heatsetting. This holder 1200 may be fitted with a hook, preferably on theproximal end, to allow removal using a snare. Alternatively, the holdermay be provided with an opening through which a hook member could bethreaded through for removal. This would enable the device to bemanually opened at a date post implantation should the need forfiltration lapse. For this embodiment, the filter element arms should beheat set in a normally open position. The holding arms may extenddistally or proximally. The free end of the holder may be fitted with arounded nose to reduce obstruction to the blood flow preventing thrombusformation and/or fibrin growth. The rounded nose may be integral withthe holder or it may be attached. The holder may also be moulded ratherthan machined from a rod or tubing. Preferably, the holding arms extenddistally and the proximal end has an integral rounded nose as thisoption will have a favourable effect on reducing irregularities in theblood flow.

FIGS. 98 to 102 show a ring type holder 1220 with protrusions 1221extending radially inwardly. The filter element openings 1225 arethreaded into the centre of the holder 1220 before being pushed radiallyoutwardly so that filter element openings are secured on theprotrusions. As the filter elements are shape set to be biased radiallyoutwardly of the apex, the filter element openings are unlikely to popout of the holder 1220, further, the space in the centre of the holder1220 can be sized so that only one filter element end 1225 can fit inthe centre of the holder at any one time.

FIGS. 103 to 105 show a variation in which a holder 1240 has theprotrusions 1242 extending from a ring 1241 and are bent distally toprovide a resting surface for the filter element 1245 openings thuspreventing the filter element ends from popping into the centre of theholder 1240 if the filter element is pushed radially inwardly.Alternatively, the protrusions 1242 may be bent proximally.

A further embodiment is shown in FIGS. 106 to 108 in which a holder 1260has a ring 1261 from which extend protrusions 1262. The length of thebent protrusions 1262 shown in the previous embodiment is extended toprovide additional security against inadvertent removal of one of thefilter element ends 1265 from the holder 1260. Yet another holder, 1280,is shown in FIGS. 109 to 112 in which protrusions 1282 extend from aring 1281 and include ridges or bumps 1283. The ridges 1283 are at leastan interference fit with the filter element openings and are preferablysized slightly larger than the filter element openings so that they mustbe forcibly pushed over the ridge during assembly thereby preventing thefilter elements from becoming inadvertently dislodged. A crimping toolmay be employed to assemble each of the filter element openings ontoeach of the ridged protrusions. It will be appreciated that any suitableconfiguration of ridge or bump that provides a permanent or removablesnap fit could also be provided. Alternatively, the protrusions mayextend radially outwardly from a central disk as the ridges will holdthe filter elements in place.

FIGS. 113 to 116 depicts a further holder, 1300, comprising a tubularmember 1302 and supporting hooks 1301 to engage with filter element 1305openings. The hooks 1301 may be integral with the tubular member 1302.The tubular member 1302 may be closed or open in the circumferentialdirection and may have a polygon or circular cross section. This holder1300 is advantageous as each filter element 1305 is held separately uponthe central tubular member 1302 thereby preventing rubbing betweenadjacent filter elements 1305. Contacting surfaces may be shaped to mateover a large surface area to distribute contact pressure in order tominimise wear and maximise durability. The holder 1305 may be assembledwith the filter elements so that the tubular member faces distally orproximally. The tubular end 1302 of the holder 1300 may be fitted with ahook to facilitate removal using a snare or alternatively, may includean opening through which a hook could be threaded. This would allowconversion of the device from filtering to open should the need arise.In another embodiment, the plurality of hooks 1301 extend from a diskrather than a tube. This holder could be stamped from sheet metal (withhooks flat) and shape set after to curl the hooks after. Either of theholders could be laser cut from tubing or sheet metal, moulded, ormachined. Alternatively, the hooks may extend in a curvecircumferentially rather than on-axis as shown.

FIGS. 117 to 132 show various split ring holders includingcircumferential arms that facilitate threading of the filter elementopenings for securement with circumferentially spaced filter elementopenings. FIG. 117 to FIG. 120 depict a holder 1320 with a central ring1321 and two circumferential arms or hooks 1322 and 1323, one extendingclockwise and the other extending anti-clockwise. There are preferablysix filter element openings (as shown) with three held on the top arm1322 and three held on the bottom arm 1323. This embodiment provides twoholding areas for the filter element openings, however, it isappreciated that one or multiple holding arms may be provided. Ifdesired, one holding arm may be provided for each filter element openingto reduce wear between filter elements and the holder 1320. It is alsoappreciated that holding arms may all extend clockwise, anti-clockwise,on-axis or various combinations of both.

FIGS. 121 to 123 illustrate another holder 1340 in which twocircumferential holding arms 1342 and 1343 are connected together by asupport arm 1341 that extends through the central axis of the filterdevice. This embodiment provides more space radially inwardly of theholding arms 1342 and 1343 to facilitate easier assembly.

FIGS. 124 to 126 show a variation of the embodiment shown in FIGS. 121to 123 where a holder 1360 has hooks 1362 and 1363 with in-turnedabutments to prevent the filter elements 1365 from dislodging afterassembly. It may be required to twist the ends of the holding arms 1362and 1363 into each of the filter element openings; however, this furthersecures the filter elements to the holder 1360 as there will be notwisting forces applied to the filter elements during use.

Alternatively, the abutments may extend radially outwardly or axially asshown in FIGS. 127 to 129. In these drawings a holder 1380 has a centralarm 1381 from which extend two hooks 1382 and 1383, with axialextensions 1383 and 1385 respectively pointing in the same direction.However, it is appreciated that axial extensions 1383 and 1385 mayextend in opposite directions. In another embodiment where the holder isformed from wire, the axial extensions have excessive length (forexample—100 mm) to aid in threading the holder through filter elementeyelets (a longer length can be held by hand rather than with a tweezersenhancing ease of assembly), after assembly the extensions can be cut toany desired length, preferably less than 3 mm. It is appreciated that asacrificial length of material may be included with any of the holdersdisclosed. This is especially true for holders manufactured from wire asone only needs to postpone trimming the additional length until afterassembly. For holders laser cut from tubing, this would required asubstantial amount of additional laser cutting and raw tubingmaterial—therefore, such a sacrificial length is not as desirable forlaser cut embodiments.

FIGS. 130 to 132 show a holder 1400 is in the form of a single holdingarm with abutments 1401 extending radially inwardly at either end. Theextensions 1401 form a non re-entrant opening 1402 so that the holder1400 can securely engage the filter element 1405 eyelets. Alternatively,the abutments may extend radially outwardly, on-axis, or a combinationfor either.

FIGS. 133 to 139 depict another holder 1420 including a central hub 1420and an outer housing 1421. The hub 1420 includes recesses 1422 for eachof the filter elements 1423 and the housing 1421 engages with the hub1420 to lock the filter elements within the holder. The filter element1423 ends may be fitted with openings or hooks to afford a mechanicalabutment between the hub and filter element ends.

It is preferred that the holder of the various embodiments interlock thefilter element ends together in a way that minimises movement of thefilter elements relative to the holder—this will minimise the extent ofwear, thus enhancing durability. The preferred internal diameter of theholder is between 0.4 mm and 3.0 mm, more preferably between 0.6 mm and1.2 mm, and even more preferably between 0.8 and 1.0 mm. If the holderis sized so that the ends of the filter elements are held tightlytogether, there will be negligible movement between filter element endsand the holder. Instead, the filter element ends and holder will movetogether as an assembly.

The invention is not limited to the embodiments described but may bevaried in construction and detail.

The invention may be manufactured from materials including but notlimited to Nitinol, stainless steel, cobalt chromium, biodegradablematerials, and/or implantable polymeric.

The proximal support hoops may be of sinusoid, crown, or zigzagconstruction. The proximal and/or distal supports may include more thanone sinusoid, crown, zigzag construction, or paddle support.

The filter elements may be shaped to provide a more uniform filter poresize than straight filter elements.

The filter cones of the devices presented are intended to point distallyin a blood vessel in order capture clot centrally in the vessel wherelysis, the physiological process in which the captured clots are brokendown in the body, is optimum. It is appreciated that the devices may bealternatively positioned with the filter cones pointing proximally inorder to capture clot in an annular region at the vessel wall.

The support frames of the present invention may be fitted with barb orhook features to further reduce the likelihood of migration.

The devices disclosed herein may be manufactured of wire material.

The devices disclosed herein may be manufactured of multiple pieces andjointed later.

The invention is not limited to the embodiments described but may bevaried in construction and detail.

The holders may be made of biodegradable material in order to affordconvertible properties to the device if desired where the filterelements move from a closed filtering position to an open position withunobstructed blood flow after a predetermined period of time.

The integral filter apex arrangements may be modified to have free endsand include openings for reception of a biodegradable holder in order tosupply the support frames in embodiments where the filter elements aremovable from a closed filtering position to an open position withunrestricted blood flow.

1. A vascular filter device comprising a support frame and filterelements, the filter elements extending from the support frame towardsfilter element ends forming an apex at which they are interconnected,wherein said apex is located at or near a central axis of the vascularfilter device; and wherein the filter elements are biased such that ifunconnected the filter element ends are located between the supportframe and said central axis when the vascular filter device isunconstrained.
 2. A vascular filter device as claimed in claim 1,wherein the support frame and the filter elements are formed integrally.3. A vascular filter device as claimed in claim 1, wherein the supportframe and the filter elements are formed from NiTi.
 4. A vascular filterdevice as claimed in claim 1, wherein the filter element unconnectedpositions are provided by the filter element shapes and the angles atwhich they extend from the support frame.
 5. A vascular filter device asclaimed in claim 1, wherein the filter elements have positions ifunconnected such that the filter element ends are located approximately10% to 50% of the distance from the central axis to the support frame.6. (canceled)
 7. A vascular filter device as claimed in claim 1, whereinthe vascular filter device has an indicated vessel size range, andwherein the filter elements are biased to have positions if unconnectedsuch that: a. when the device is constrained in a vessel which lies inan upper sub-range of said indicated range, the filter element ends arebetween the central axis and the support, b. when the device isconstrained in a vessel which lies in a central sub-range of saidindicated range the filter element ends are approximately on the centralaxis, and c. when the device is constrained in a vessel which lies in alower sub-range of said indicated range the filter element ends extendthrough said central axis.
 8. A vascular filter as claimed in claim 7,wherein the filter elements have similar maximum strains in situations(a) and (c) when the filter element ends are interconnected.
 9. Avascular filter as claimed in claim 7, wherein the filter elements haveapproximately equal maximum tensile strains in situations (a) and (c)when the filter element ends are interconnected.
 10. A vascular filterdevice as claimed in claim 1, wherein the support frame comprises aproximal hoop, a distal hoop, and interconnecting struts.
 11. A vascularfilter as claimed in claim 10, wherein the proximal hoop has peaks andthe filter elements are connected to the support at or adjacent distalpeaks of the proximal hoop.
 12. A vascular filter device as claimed inclaim 1, wherein the filter element ends, the filter elements, and thesupport frame are formed integrally from one piece.
 13. A vascularfilter device as claimed in claim 1, wherein the filter element ends areformed integrally to provide an integral apex.
 14. A vascular filterdevice as claimed in claim 1, wherein the filter element ends areinterconnected by a holder.
 15. A vascular filter device as claimed inclaim 14, wherein at least some filter elements have eyelets and theholder is trained through the eyelets. 16-40. (canceled)
 41. A vascularfilter device as claimed in claim 1, wherein the filter elements areinterconnected by interlocking features.
 42. A vascular filter device asclaimed in claim 1, wherein the filter elements are magneticallyinterconnected. 43-57. (canceled)
 58. A vascular filter device asclaimed in claim 1, wherein the filter elements extend towards two ormore filter apices. 59-70. (canceled)
 71. A vascular filter devicecomprising a support frame and filter elements, the filter elementsextending from the support frame towards filter element ends connectedto form an apex, wherein the support frame comprises a proximal hoop, adistal hoop, and interconnecting struts extending between the proximaland distal hoops, and wherein the distal hoop comprises an array ofunconnected V-shaped or m-shaped struts.
 72. A vascular filter device asclaimed in claim 71, wherein interconnecting struts comprise an array ofproximal connector struts and distal extension struts and, whereinfilter elements are connected to the support frame between the distalextension struts.
 73. A vascular filter device as claimed in claim 71,wherein filter elements are connected to the support frame between theinterconnecting struts.
 74. A vascular filter device as claimed in claim71, wherein the interconnecting struts comprise an array of twinconnector struts.
 75. A vascular filter device as claimed in claim 74,wherein an opening is formed between each twin connector strutseparating the proximal support hoop into an array of the v-shaped orm-shaped struts.
 76. A vascular filter device as claimed in claim 71,wherein the apex is located at or near a central axis of the vascularfilter device, and wherein the filter elements are biased such that ifunconnected the filter element ends are located between the supportframe and the central axis when the vascular filter device isunconstrained. 77-96. (canceled)
 97. A method of manufacturing avascular filter device comprising a support frame and filter elements,the filter elements extending from the support frame towards filterelement ends forming an apex at which they are interconnected, whereinsaid apex is located at or near a central axis of the vascular filterdevice; wherein the filter elements are biased such that if unconnectedthe filter element ends are located between the support frame and saidcentral axis when the vascular filter device is unconstrained, whereinthe method comprises: cutting a tubing, and expanding the tubing.98-108. (canceled)